Morphology of Psilotum

Morphology of Psilotum

1. Introduction to Psilotum

Psilotum belongs to the family Psilotaceae and order Ophioglossales of the vascular plant division (Pteridophyta). It is the only genus of the family Psilotaceae. In total, there are about 18 species of Psilotum belonging to the genus, out of which 2 occur in India viz., P. nudum and P. triquetrum. The plants of this genus are popularly known as whisk ferns, as they resemble the whiskers of some animals. Psilotum species are unique plants with small, leaf-like stems that absorb water and nutrients. They are classified as vascular plants with xylem and phloem, but lack most features common to vascular plants. Unlike other vascular plants, species of this genus do not have true leaves, roots or flowers. Instead of conventional green leaves, they have flattened photosynthetic branches that perform photosynthesis and help in the growth of new branches. Flora of Psilotum exist in two different forms. Some are terrestrial, found in rainforests. A few species of this genus seem to have poor or no detritus-seeking mycorrhizal symbionts. They have a limited distribution and occur in moisture-retaining rock hollows, whereas other plants growing in rainforest canopy are dispersed and common. Psilotum species are highly drought tolerant. In rainfall induced drought, off the rainforest canopy they roll up their flattened branches, curl up and lose less moisture. Occasional prolonged drought can kill all terrestrial individuals but rootless specimens persisting on the canopy of supporting plants endure drought. In near natural rainforest, Psilotum is abundant but may dominate tree ferns on exposed granite where canopy plants are few. This supports the notion that it’s an incidentally salt-tolerant fern that flourished after rainforest canopy clearance and for long survived in relict patches of rainforest. Psilotum species in semi-arid environments growing on rock walls and in shady crevices have a similar habit. Psilotum triquetrum and P. nudum are the two species that people are familiar with. Since the discovery of bloom and fruit, Psilotum has remained a favorite subject of study because of its bizarre reproductive biology and tropical distribution. All seminal ferns and their ancestors are suspected to have either branched or unbranched morphology. Peels of a die and take-home die cast based capsules similar to those of Psilotum appear to have an ancient origin, previously unknown to have been surveyed in modern plants. The known Psilotum inflorescences rust-exclude spherically flared naked bracts. Certain ancient inflorescences sired by a small flowering shrub resemble Psilotum. Direct relevance of these diagenetic structures and data, and old genes, is highlighted to spark interest in Psilotum itself and its ancient past.

2. Historical Background

The phylogenetic position of Psilotum, whose morphology is examined here, is the sister group to all other extant vascular plants. On first appearances, Psilotum has such simple morphology that it is often commented on as resembling a poorly developed herbaceous plant or a fern held in the developed juvenile stage of a gametophyte. Certainly, none of its organs can be regarded as homologous to the leaves, stems, or roots of angiosperms or other vascular plants. Psilotum possesses no true leaves; its ‘leaves’, which are merely small flattened scales, are situated on the stem in whorls of 3, 6 or more in the youngest part. It has no aerial roots; the thin, hair-like filaments are rhizome hairs, derived from the skin of the underground stem, and cannot be regarded, in anatomical terms, as roots. There are no traces of vascular bundles in them.

A part of the stem which bears sexual organs develops whole from these hair-like parts, and grows erect above ground. The young stem, which is cylindrical in cross section, resembles a certain plant; but it becomes flattened and deeply grooved afterwards. Three ridges are produced on the upper lobe, and the middle, the lowest and the upper ones are dorsal, lateral and abaxial sides of the stem, while the steeply grooved sides are considered as adaxial sides in older plants. A transverse section of the grazing portion of the stem revealed almost the same structure as those of lower vascular plants or their relatives.

There are no distinguishing features sharply separating Psilotum from the lower vascular plants. Its morphology is so simple that it is often regarded as a representative form of the connecting link between bryophytes and higher vascular plants. Fossil remains of Psilotum had long been known, but a large number of rich and interesting fossils were reported from the Mid-Carboniferous and even-rooting carbonaceous shales, although the findings were soon forgotten. Observations on attempts at regeneration of slice twigs of Psilotum revealed two remarkable facts. It is demonstrated that cut organs were not only fully regenerated but that their function was the same as before experimental treatment. Epidermic hairs, at first undistinguishable from those of the ground tissue, were transformed into foots and a well developed capsule wall.

3. Taxonomy and Classification

The relationship between the Psilotum genera and other groups of vascular plants has piqued the interest of numerous researchers spanning multiple generations, a situation that appears destined to persist for many more. While it may be rather impractical to examine the numerous scientific issues and philosophical implications this involves, some general observations will be made. Over the past one hundred years, there have been few generations of plant biologists that have not significantly advanced knowledge of the Psilotum family. A few generalizations, however, seem appropriate: 1. The basic morphology and anatomy of Psilotum were adequately and even thoroughly studied up to 1930, forming a basis for work in many areas pertaining to its biology. 2. The basic morphology and anatomy of Psilotum should be revisited for two reasons (a) because of the difficulty with those study based largely on the earlier literature and (b) in order to indicate the unusual advance in knowledge and the difficulty in interpreting some aspects of it. Ideas about classification in 1920 have not changed greatly, but there has been an increased recognition of needed study in some related areas. 3. A few pointers of this nature on the general biology of Psilotum are included. Because of its apparent structural simplicity, some of these points concern morphology and anatomy, while others involve the more chemical and ecological aspects of the plant.

The Psilotum genera were named “crown-less” and “bristle-typified scape” plants in pre-Fitzgeraldia times. Such names, while reflecting some morphology, were far too descriptive and lacking in historical and biological considerations. Psilotum and aidia are preferred as names for the two genera in the family Psilotaceae. The name Psilotum means “bare” or “naked”, and is a most appropriate name for the genera embracing plants that may lack leaves, true roots, and other structures usually characteristic of plants. Although historically used in various ways in connection with various plant designates, it has now acquired a much narrower bio-historical meaning, and is best used in that sense. The name Pseudoslerotia was used for the scape of one of the mosses in pre-plant vascular times. Like Psilotum, it is a good botanical name, being readily understood in but a few languages. It is here preferred for a family name of choice among plant nomenclators.

4. Morphological Characteristics

The above-ground stems of Psilotum are cylindrical and pale green. The length of the stems varies with location but can be as long as several meters. Stems are usually branched in the upper or middle portions, in a forked manner. Each stem may produce one or two branches at a junction to form a fork. The first branch diverges at a narrow angle of 19 – 53°. The next branch is then formed in the first internode which results in the formation of a fork. The appearance of the stem is affected by the type of lateral branch and the branching pattern. The stem node is expanded, and slight fluctuations may exist. The distance from stem top to stem top is determined by environmental factors up to six in a chain. The total growth period is about two years. At the site of major lateral branching, the shoot apex persists as a operculum with a total diameter of 4–5 mm. There are also several unbranched shoots in the vegetative population. However, this morphological hypothesis is still incomplete.

Epiphytic members of Psilotum attach to substrates such as trees or rocks. Psilotum, on the other hand, primarily grows as a terrestrial plant in humus-rich soil. Fertile members, such as grape-sized catkin-like spikes, arise from the apices of matured plants. These primary stems are cylindrical and pale green, forming an erect and ascending habit. Paired lateral branches diverge upward, forming forked structures. Above branching sites, nodes are slightly thickened. The length of the above-ground stem can reach 3 m, with the height of the vegetative above-ground stem at about 135 cm. Stems vary from unbranched, four to five branched, to more complex patterns. The top portion is always branched, while the lower is branched sporadically. However, the majority of stands are not branched below 30 cm.

In addition to leaf structure, the anatomy of the stem was also investigated. The shoot axis of Psilotum is cylindrical and pale green. It is usually cylindrical or striated, occasionally with lighter grooves. Branching is generally in two planes with three or four orders. Branches occur in pairs at an angle of 30 – 70° from the main stem. Each primary branch may divide into further branches. Stem width varies with the location of the shoot and its growth state. Continuous growth is observed, usually extending to 97 ± 29 cm (maximum 267 cm) for vegetative shoots, longer for fertile shoots. An actively growing stem with a total height of over 6 cm has the apex concealed in the thick white sheathing of the stem epidermis. A light green cylindrical or flattened filament, 6–10 cm or 4–5 cm long, may be present above the terrestrial part.

4.1. Stems and Branching Patterns

With approximately 400 described species, Psilotum is a genus of remarkably simple plants, with one or two species present in each of the hot or warm areas of every continent, with the exception of northern Europe and North America. The Ecological Zone encompasses the Mediterranean regions of southern and southeastern Europe, western Asia, and northern and western Africa. Despite the remarkable ability for such plants to colonize and adapt to such a variety of environments, the genus was only recently recognized as being polyphyletic and with an important disjunction between various clades. Although some morphological data supports this notion, no comprehensive phylogenetic analysis using a large sample of different species and several gene loci has been published in over a century (Coudert et al., 2017).

Due to the simple morphology and small size of psilotophytes, preserved specimens of Psilotum are better left in whole mounts. A simple glass stir rod and razor blade are all that is required to split samples. Other workers have widely used the straight edge of a talc plate or the edge of a fountain pen for this purpose. A similar technique is equally useful for monocot lignified tissue. If prepared carefully, a simple slide-scanning camera may be used for field studies. Later addition of cortical morphology images can provide a circular view. Examinations of characters vary widely in method quality; figures are often limited and unclear.

Psilotum rastratum is the type species for the genus, distinguished from P. nudum by its seemingly grouped leaves. Archaeosporum were based on exarbicate spores and four anchor cells, as distinct from the more usual pattern. Both genera were elevated to family rank, but the later publication forgot to rename Psilota. Several herbarium specimens claimed Pseudobryum, but these quickly resolved to Psilotum. Pseudobryum differed from Extinct by its leaf characters, and these groups were described as incertae sedis.

4.2. Leaf Structure and Arrangement

The sterile leaves of Psilotum (Psilotaceae) are unusual among ferns by being scale-like and generally lacking a vascular supply. In ferns with leaves, leaf gaps occur only in association with curtains of vascular strands corresponding to the leaves. With scales such as those of Psilotum, intervening vascular strands without periodicity are thus a possibility. Studies of different fern taxa suggest that Psilotum can be effectively studied in terms of leaf structure and arrangement on plant specimens itself. Morphology is well-defined and distinct in reference to broad plant grouping and enables both an illustrated description of the structure of leaves, leaf insertion and arrangement, stipules, and trichomes of P. nudum, and a comparison of variations of general morphological features of leaves among several species within Psilotum (Psilotaceae). A basis for the understanding of taxa in botanical terminology is also presented, frequently used technical terms are defined, and morphological features of Psilotum in general are contrasted with those of similar ferns. In the context of fern leaf investigation, discussions on terminological and typographical conventions, as well as a caution against misinterpretation of ferns as foliarised lycophytes often seen in morphology texts, are included. Studies of leaf number and distribution are rare in ferns. While fern leaves can be highly varied, studies of leaf base and leaf surface morphology relative to arrangement have revealed leaf pair inclination and subsequent leaf self-shading affect growth at the leaf base in some taxa, with broad environmental implications. Other studies have explored periodic associations between a fern's hydrological environment and leaf blades, leaf bases, and leaf orientation. Despite a fossil record of leaf-stacking adaptation in swamp-dwelling ferns, limited comparative study in extant ferns has been undertaken. A clear definition of foliage arrangement on an organism is crucial in understanding fern ecology and evolution (Vasco et al., 2013).

4.3. Rhizome and Root Systems

With the exception of the sporangium-bearing petiole bases in Sporogonium, the morphology of all the organs of Psilotum has been described in detail. The rhizome systems that were present in the fossil plants have a morphology that would not be classed Adiantum and which would be functionally analogous to the adaxial roots of that genus (J. Hetherington & Dolan, 2017). Most present-day vascular plants have a root/ shoot dichotomy (the roots being the organs developing from a rhizome below ground) lacks inherent polarity and may be formed of a set of modules (branches) of contiguous similarity. However, the initial branching and the first addition of a module to a basal branch is a step which is more or less precociously lost in some plants. Such may be regarded as macroplants that have acquired the capacity to grow as a series of similar modules (paraclades or annomodes).

In this form the plant would be similarly billed a budget to attempt to develop a symbiosis with fungi, even though the time available for such a process would be limited in comparison. Root form/growth behavior is an integral part of all growth forms and tricks or cheats that compromise root development do so at some cost, never just offer a free ride to you in terms of moisture or nutrients. In the case of Adiantum, for example, the benefit of all of this is economically the establishment of a new copy of the parent plant at a distance. In case that new copy does get translocated it is nevertheless climatically limited in Walt’s world by the adhesion and frost action of detrital soil particles after wetting.

Because of the way that gametophytes of Adiantum are limited by the distribution of its spores it is difficult to determine the biogeography of what must have been its massive initial dispersal. However, this, and the point made earlier about the improbability of entire equatorial land masses being filled with a single genotype species suggest that the initial dispersal routes were easy and sourcing populations wide. On the basis of attempts to estimate the two ages of living groups of vascular plant a time scale is available for the creating processes that followed their initial dispersal. Since this present age of the Recent is by definition 1.0, the most ancient land plants that first events are estimated to be about 400 million years.

5. Anatomical Features

Siphonogonium sphagni (Mutz) Škerničeva, M.D. Burch. and Ploeschnickelobris svamini Škerničeva, V.W. Kapp, Škerničeva, and J. Tam YS I, unique species of Siphonogonium, previously known and half-elucidated plants, are described from Sweden and Botsvana. Their sporophytes were found at Bogstahojdsmosse, Svedjev, Gotland Is., Sweden, and localities very rich in epiphytic flora on the top of the Platfontein cliffs of the Tswapong hills, Kweneng district, Botsvana, southern Africa, respectively. Preparation of fresh sporophytes has revealed important morphological characters and structures, including a structure not before seen in Siphonogonium and basal parts of capsules in bigger scale and more detail than shown by the earlier authors. Despite imaginative explanation of the derivation of previous terms from those used by Forkel for capsules of the well-known swamp plants, which share its structural resemblance and character captured by Siphonogonium as dissected brickwalls in teetering ruins with scattered debris, unduplicable feature, in which rows of cells are abuttal-joined with each other, can still be captured by a term dealing with plant structure and naming instances of plant structure as testimonies of ancient architecture. The two species are described as new to science and the nomenclature and structure of the genus are elaborated compared with what was previously known (E. Newton & Robinson, 1994). Unusual and unique anatomy of peristome of Distichium capillaceum (Hedw.) on developing new capsules and diplostichous arrangement of leaf cells in two genera of native fern-leaved mosses with abaxially-saddle-shaped leaves are described from Papua New Guinea, Indonesia. Efforts were made to explain and comprehend the anatomical features as seen on observing optical sections of developing capsules and moss leaves under the dissecting and light microscopes. Elucidation of these peristome anatomy first to show how rise to and against outside the Upper Australia area and resurfacing in Papua New Guinea-Australia area through St. Helena Island in Pacific Ocean, features on leaf cells and of tips remained double row early differentiations after match and rapidly switching to collateral rows upon attunuation and finally reverting to one of the two lineages with stable but quite different identity feeding most intricately into the broader family are issues in urgent need of attention before origination, evolution and decimation of the entire clade with distinct moss flora on the island in the Pacific get formally understood.

5.1. Cellular Composition

The cellular structure of Psilotum is remarkably simple compared to most terrestrial plants. The basal part possesses a rhizome surrounded by a colorless root system that diverges from its surface, somewhat resembling the roots of ferns. However, because of their simplicity, rhizomes and roots do not offer much morphological variation in the characterization of Psilotum populations. Adaxially and abaxially viewable leaves of the dichotomous and tapelike aerial stem are remarkably similar, with only an increase in epidermal cell wall thickening and stomatal cells on the jaspe color surface. The stomates were composed with similar numbers of guard cells and were regulated in size by inward- and outward-aspiration mechanisms of the colors of Psilotum leaves. Edaphic-specific adaxial surfaces of leaves, however, were slimmer, eyeless, and possessed more large stomata compared to those of light-colored leaves. Aerial stems were cast into two types based on the basal leaf or branch width. The value of 13 and 56 mm defined these as slender and stout stems, respectively.

Scanning electron microscopy revealed a wide variation in hesperidium density between pink and yellow or green fruit colors of Psilotum. Specimens of yellow or green fruit colors were morphologically similar and may be considered as one fruit color. Differences in the shape, size, and morphology of the scales could be used for identification. Fruit shapes were oblate sphernoids and differed most notably in the area of independence of the radial tubercle crest on the surface. In purple color fruits, differences in the color of the surface were noted with the aid of differentiation of scales studied herein. Scales of decayed purple fruits were dehiscent, and typical features of scales of dull-colored Psilotum fruits were taken as note-worthy characteristics specific to this group. Shape, morphology, and surface color of the fruit were also acquirable features that could be observed in a field setting.

5.2. Vascular System

To reach interior tissues two groups of 2 to 6 pericycle cells are traversed and both the endodermis and pericycle also have typical fibers. The culm’s vascular system in the approximately 85% complete portion of the shrub has a comparatively simple construction and is referred to as Type #1 (William E. Stein & B. Beck, 1992). The stems consist of a widely dilated, hollow, culm comprised entirely of parenchymatous water-storage tissues. Each rib is 20 to 42 mm in transverse diameter and is composed of abaxial and adaxial flaviform laminae overlain by a lower epidermis and an upper epidermis. The rib cross-sections display topographic and vasculature heteromorphism within the laminae and between the ribs. These issues must be addressed for a proper morphological description of the shrub and a thorough understanding of the evolution of flowering plant anatomy. Simple, polysiphonic sporangiophores were produced by a plant resembling none currently extant. Such a plant would have resembled an aerial growth form poised mid-way in the evolution of both sporangiophores and lycopsids. These stem bases support either a normal axial bifurcation or an unusual phyllotactic pattern of bifurcation. Fibers also occur in the ribs which have a different fibrous pattern than those typically occurring. It is suggested that, if not rudimentary jointed strobili, these vegetative parts resemble what the earliest flowers would have resembled during their transition from stroboli to flowers.

5.3. Reproductive Structures

The completion of the life cycle begins with the formation of the egg, which develops from the ventral cell. In the egg of Psilotum, wall formation begins in the mature spore by the deposition of outer and inner walls at the two poles of the spore's protoplast. The outer walls are thin, whereas the inner walls are thick. The first division is transverse to the long axis of the spore; and the small (upper) cell or apical cell produces a dome, the domical cell. Similar wall deposits are observed in the apical cell of the gametophytic stage. At this stage of development, the spore is about 135 μm long and 150 μm wide. After this division, the anticlinal wall of the dome thickens and becomes ornamented.

A concave upturned, basal cell is produced after one more division of the dome cell. This basal cell is relatively larger than other cells, similar to the basal cell of the gametophyte. Of the two cells produced by the further apical division of dome cell one receives the basal cell and grows very slowly, so that a flat and disc shaped development is resulted. Complex anatomy is observed only in Psilotum triquetrum and Perameceum decumbens due to the undulate and erect nature of the gametophyte. The rest of the functional and developmental characteristics of the egg types are similar. Though specialization in the two types of egg has been observed, any additional complexity is attributed to external nature and current environmental conditions (Vázquez-Pérez et al., 2014). Taking into consideration of the evolutionary equation as an expression for design the spore express the most primitive and elongated egg and covered like a semisress cup like structure.

Later on they are predominantly reduced to phycocuper then to PHC of similar or lesser coats thickness. All these illustrate a change from telomic and open to pinnate and closed forms. At the stage of functioning fossil forms are preserved from the lower Devonian onwards. Midalgo and Mississippian strata yielded P. mornay. The Cretaceous Po and the recent ones have been assigned to the same group. Varied life forms are found from silver whitish, cream and light yellow to bluish green, dark green and olive green (Grolle, 1993). Thus examples like Psilotum and Polytrichum with more dissimilar colors, textures and shapes demonstrate the widest variety of reproduction.

6. Developmental Morphology

Attaining similar evolutionary outcomes in independent lineages through similar but not identical solutions is known as convergent evolution and can be found across an impressive range of organisms, from prokaryotic to eukaryotic life forms. Nevertheless, convergence is often quite selective, and many biological structures for which the principles of self-organization have been established independently show no noticeable resemblance. Alternatively, Wallace’s line – the biogeographical barrier that separates two neighboring areas with markedly different floras and faunas – which has held true for some plants and animals, does not necessarily apply to others. There are examples in which very closely-related organisms are completely disjoint phenotypically, ecologically, and physiologically, while distantly-related organisms can look very similar and function in the same way. Thus, it can be stated, in an evolutionary sense, that morphological phenotype is kept throughout the years, though molecular machinery may differ greatly across species. If morphology is to be conserved, so must the underlying molecular processes.

Mosses acquire their distinctive morphology throughout two different phases of plant development: the sporophyte and the gametophyte phase of their life cycle. In land plants, the diploid sporophyte generation usually develops from an initially mitotic zygote and consists of a foot, a stalk, and a produce dehiscence–triggering pores, rice-like elators, or wind-borne spores. The filamentous or fruticose morphology of reproductive structures is one of the simplest morphological designs of the gametophyte, while complexity is a generic character of the gametophyte during the evolution. Complexity of the mosses is measured on the basis of number of phyllids and types of the structures (leaf) (Kirbis et al., 2020). The selected species for complex and simple morphology are P. patens and Psilotum nudum. Developmental morphology of the mature P. patens sporophyte consists of a single unbranched seta and a spherical capsule. The developing capsular structures have been classified into three types based on a comparison of the developmental processes. Three capsular morphogens have been defined at the capsule mid-ventral position, the cap with its own suture, and the deposit basal cells parallel to the capsule using confocal microscopy, leaf clearing, and SEM. Development of the whole capsule in P. patens is ascribed to the progressive growth.

6.1. Germination Processes

To assess spore germination processes, ferns must be able to respond to physiological signals, and conditions must remain relatively constant within the testing period. Collected spores must thus be prepared in such a way as to prevent further physiological changes within the spores (Alejandro Gorrer et al., 2018). Ideally, spore preparation would take place under the same conditions as storage, but widespread spores would remain only as localised, other ferns must also be collected, preservatives must be prepared in large quantities, and all fern growth stations must prepare solutions ahead of time. As a result, spore transport was either carried out on the day of collection, or overnight in such a way as to remain relatively constant from collection to transport. Loose spores of P. nudum were made available for experiments.

Prior to any experiments, sporophytes of P. nudum must be grown. Allowed to grow for approximately two months, sporophytes began producing sori. To evaluate the reproductive success of sporophytes, a minimum of 5 sori must be made available for each experiment. Sorii must be placed in paper envelopes and allowed to dehisce a minimum of 72 hours over a heat source. Allowing for dehiscence in this manner provides both standardisation in the collection process, and sterilisation of collected spores. If more than 5 envelopes were to dehisce in this manner in any day, the opportunity to cover the fragments of multiple species would be lost, as only five envelopes could be easily used, and if any one envelope could not be used, then the collection of spores would be wasted. Moreover, since the dehisced spores would have been exposed to the air and more susceptible to contamination for an extended and variable period of time, any one envelope would be risking contamination of spore germinability assessment if not covered and processed on the same day as dehiscence.

6.2. Growth Stages

In Psilotum, growth stages have not been described in detail. Certain characteristics apply to growth stages in Psilotum sp. seedlings: (1) a juvenile stage extending from lower leaves being 3–5 mm long and 1 mm wide, through (singly) branched plants where branches are shorter than stems, to plants about 2 cm tall; (2) branching occurs only in the aerial system until a basal branch (the first, relatively long branch) develops and roots are formed; (3) secondary branching usually occurs from preformed leaf scars, which results in ‘whorled’ branching; (4) floral buds develop at or near branch tips in mature individuals; and (5) floral morphology is combined with leaf (bract) morphology (J. Moore et al., 1991).

Fern growth stages may include four stages: (1) juvenile, or ‘fiddleheaded’ (similar to that of vascular plants); (2) radiating and expanding, or aged juvenile; (3) aerial frond differentiation, where leaves stalkless and fragmented; and (4) adult stage, where air-born fronds are produced. For Psilotum sp., the initial stage may be developed until it is 2 cm tall without branch or root formation. Leaves rarely increase in size above stage 1 (15 mm long); all 1 mm wide; and developed exclusively near the tip. Significantly, Psilotum bi-or tri-leaved erect individuals, which are juvenile ferns, also have neither remarked-branch nor root, although they are several cm tall. Early herbaceous forms are not markedly bushy in aerial growth.

7. Ecological Adaptations

During the Cretaceous, Psilotum's affinity other plants significantly declined possibly due to detrital conditions that destroyed silica. Its ability to acquire nutrients from a detrital medium has to be linked not only to preservation and evolution but also to the basic ecological adaptations of the genus still common among its sporophytic relatives. Accordingly, it has been suggested that most living species of Psilotum are no longer able to complete their life cycle in an open and extraproductive habitat because of a catastrophic depletion of potassic resources from such environments (Huttunen et al., 2012). This ecological shift would facilitate the emergence of the detritophile herbaceous desert and the origin of the genus Equisetum.

Moreover, it is suggested that monitoring the effects of human-driven changes of biogeochemical conditions on the occurrence of living Psilotum allows extending to the Jurassic–Cretaceous transition. Gradual ecological drying would promote the contemporaneous extinction of some of the more recent species and the detritophage–herbivore transition. The latter would permit the evolution of herbaceous deserts and ultimately for Psilotum to be preserved only in detrital crevices of forbidding climatic regions.

Devising and implementing a reconstruction protocol of juvenile sporophyte morphology in Nota is likely to be an interweaving of a methodological investigation with heuristic one. If pseudoeventful steps are devised and a compositional database of 3D geometries formatted, the extraction of previously unseen semi-automatiy numerically-measurable structural traits is feasible both at the strobili and stem levels. Further investigation of their evolution is likely to result in informative knowledge both on the morphological evolution of Psilotum and possible mechanisms of this evolution in other low-information but data-rich desert systems, with wider audiences in natural science.

7.1. Habitat Preferences

The habitat preferences of Psilotum varium will be considered first. Next, the morphological variation of plants naturally growing on different substrates and in different habitats will be discussed. The occurrence of the two varieties of P. nudum in disturbed (as well as, naturally) occurring habitats will be addressed. Finally, anthropogenic changes in the distribution of Psilotum in the mainland tropical America will be considered. All Psilotum species grow or have been recorded from acidic terrains. When offered the choice of growing in non-acidic peat or acidic soil, all species of the genus would habitually grow in acidic peat, regardless of the spontaneous growth of swamp species such as fern. This survey found that 90% of the taxa recorded naturally on acidic environments had this preference. A similar situation occurs with mosses growing on acidic plantation left after palm oil trees fell on them. These mosses grow luxuriantly and are mostly acrocarpic, comprising 65% of the total recorded samples, which include members of the Campylopus and Ditrichaceae. Some Ditrichaceae are restricted to this type of acidic habitat.

Three samples of P. nudum from Brasil found growing in acidic logs were cultivated in Te loam soil of pH 6.2 with nutrient disturbance for two years. Plants of the first batch died quickly while plants of the other cultures with richer nutrients were somewhat better. The surviving plants but displaying various abnormalities were mostly flat and even when upright were rarely larger than a few millimeters long, indicating a marked intolerance for increased nitrogen (Kuc, 2000). There are also chemical indeterminate effects. On planting P. nudum or the variety with distinct filiform shoots, all plants died within half a month of ammonium sulfate treatment while P. nudum was more dramatically affected than P. nudum var. fluitans. Other human managements immediately followed the inundated chemical substances including sodium hydroxide, strong detergents and herbicides, all eradicating any remaining traces of these two Psilotum species.

Psilotum nudum is distributed throughout southern Africa, most of India, Sri Lanka, much of New Guinea and Melanesia, most of the islands of the Pacific and sidelands of the Mexican mountains. Psilotum nudum var. nudum is only recorded from the Caribbean area of the middle and upper tropical latitudes in North America. On the continent south of Mexico, it only reaches Guatemala, exiled to St. Hilarion Island and the Breakers on the east in Florida. The other variety is also found nowhere and is also absent from Jamaica and much of the Lesser Antilles. In neither of the two island archipelagos are there records of other Psilotum. Within tropical and subtropical latitudes, Psilotum is displaced by equivalent eusporangiates.

7.2. Interactions with Other Species

Psilotum nudum and P. complanatum are often found growing in extremely barren, usually relatively dry situations. Their habitats include road cuts, rocky hillsides, sand piles, and other open situations where there is little or no competition from vascular plants. However, they often grow among mosses and lichens and may be outcompeted by soil-building mosses on boulders in a few cases. Parasitic fungi have been recorded on Psilotum, but due to the limited number of infected specimens, further research is required to ascertain their precise roles in the lives of the plants.

Psilotum frequently has epiphytic and/or endophytic fungi associated with it. Records of aerial mycelium, individual fungal hyphae, or rhizomorphs growing in small cavities or along the aerial stems are common for specimens from diverse areas. Moreover, from limited data on the mycoflora of each of the two species in these genera across various districts, it is evident that P. nudum is more varied in its diversity of fungal associates than P. complanatum. This might be due to the larger size and more divergent microhabitats of this species. Numerous fungi were discovered to be growing on or associated with these fossils, some of which had never been recorded as living on Psilotum in recent times, even some having never been previously described. These findings suggest that epiphytic fungi tended to evolve before the extinction of the Psilotaceae on the continent, forming a mycoflora similar to that of P. nudum in southern China. They might have contributed much to the pest status of this group of plants before their demise.

8. Evolutionary Significance

In 2016, a series of two-dimensional sections through the recently collected fossils of Psilotum were presented to the Society in the British Museum. In the following year, it was published as an especially large paper which integrated the knowledge acquired previously (D'Ario et al., 2024).

8.1. Phylogenetic Relationships

The placement of Psilotum within the vascular plant phylogeny has long been contentious. Several phylogenetic analyses of morphology lend support to an early-diverging line at the root of the vascular plants or sister to the lycophytes, while others recover a position nested amongst euphyllophyte ferns. The support for anything other than a basal position generally arises from analyses that employ indicative characters such as presence/absence. Its close relationship with Tmesipteris is well supported.

In contrast, Equisetum nodosum, although somewhat aberrant for the group, has morphological characters that are more or less consistent with monilophyte relationships overall (G Karol et al., 2010). There has been some retracing of steps concerning the nature of the more basal clades of vascular plants, particularly regarding lycophytes and euphyllophytes and their relative ages. There are still a number of poorly supported relationships below the family and even genus level among the ferns.

Lycophytes are well characterized nationally and globally with archaeological and structural records extending back 450 million years. They are now composed of three widely separated clades: the Isoetaceae, Selaginellaceae and Lycopodiaceae. Current research examines several aspects of the family, with emphasis on molecular phylogenetics, character evolution and the origins of heterospory and secondary xylem. Morphological character evolution is considered the strongest test of phylogenetic hypotheses. The majority of fossils attributed to the group have not been assigned to modern clades, but some are also known only from imprints lacking cellular anatomy. The common species, whose anatomy and reproduction are intensively studied, appears to have rendered much less datable information than currently available on tropical species.

8.2. Evolution of Morphological Traits

Comparing traits observed in the present and traits inferred as ancestral is useful for hypotheses relating to trait evolution, but still requires understanding how these traits are conserved. Morphology is the evolutionarily most informed by transition pathways, influencing how traits would evolve given candidate origins and derived forms. Some transitions appear to be relatively easy, with rules likely governing many aspects of how these traits come together to form structures that function for the plant's life history. The successful, long-standing modes of life represent trajectories through morphology space, folding into better learning starting points for new environments than where they began (Coudert et al., 2017). Comparisons of the transition pathways can yield insights into developmental and environmental roles in morphology.

The morphology of Psilotum is being mapped into descriptors of spatial domain and resulting embryonic movements. This trait space will be compared with the distributions of the morphology of morphospecies guessed a priori, and those observed in the fossil record. The aim of this project is to be able to visualize psilophyte morphologies at any stage in the fossil record capturing the morphology of most of this group's diversity. The first research is how the proposed descriptors path developable state trajectories, focusing on lucid and unambiguous demonstration of development onto traits that have previously been inferred. The next step is to sample and classify a data set broad in both temporal and morphological diversity as described above. Comparing the path descriptors on the data set to capture their relationships and how they are distributed across trait and time is thought-provoking (Kirbis et al., 2020).

This systematization framework for pioneering morphologically dividing a clade before the data set's individual taxonic morphology source can be critically examined against other sets. Further characterizing mappings directly from development to morphology may also uncover the last ways such data can be productively compared, relating development to morphology more inclusively across the plant kingdom and potentially lineages. Ultimately, these projects address foundational questions in plant and evolutionary biology based on an ascendant phytoecological and phylogenetic lineage.

9. Comparative Morphology

Shared contenders of the living expression of organisms must consist of approximately the same non-sympatric species, genera, families or higher groups. As a species on a phylogenetic tree becomes “eternally” extinct through the death of all its living individuals, its complex of living systems of organisms decays to a common territory of functionally degenerated features. The living expression of a group trends to simplify morphologically and thus may share with many other complaints permanent GMOs that also represent a differential degenerative organization. Fossil and coeval judging or reference observations are required to properly establish such organizations. An ensemble of functionally complementary morphological features, often so complex that only a few can remain recognizably expressed in a new ensemble, becomes systemically categorized and geometrically recreated. This process affects all groups of different hierarchical orders from higher morpho-systematic entities (species, genera, families) to lower functional systems (intrageneric or intrafamilial character associations). Regarding form, paleontological or ecological observations would with probably equal success affect deep and shallow time.

Widely distributed simple plants may remain forever functionally sufficient in marginal ecosystems. On hypothetically lengthy time scales this functional simplicity advantageously suggest a long-term stasis of form. If so, an assumption of similar coeval GMOs would help to collectively picture a past degenerative organization. Two widely distributed simple plants of the Fern class, Polypodiopsida, are considered here: hunga vine cladonian Psilotum and all of its kozoelas; hardy, leafless and rootless captures of uniformly branched arborescent Cyatheaceae, sad bathospheric old-world natives invader-free in now-moderate climates. They are explored with the same conceptual and methodological associations as illustrated a similar demise scenario for Flames whisk ferns (Yañez et al., 2019). Comparatively graded judgments may reveal a deeper time of practically non-evolving living simplicity.

9.1. Comparison with Other Ferns

The analysis of morphology of above-ground and underground organs basing maps of escarpment near the Shakan River is presented. The morphological adaptations of niche population are reflected in shape of leaf of sporophyte and structure of underground organs of their gametophyte. These leaf forms changed considerably but some of their "plastic" characters remained, the plasticity of such ontogenetically young organ probably being initial factor of their ecological success. They capture tropospheric moisture in addition to rainwater for growth and reproduction.

The outmost form of this leaf is disturbed greatly comparable to typical yellowish color of suberisation, structure. These organs have adaptation for storage the water in elevated environment (lack of air space, slope structure), and capture moisture (form, place of construction, multi-length, layer, and dense net of pores). Due to the spherical structure, competent resistance to mechanical crushing is provided. These rosettes of leaves are determinate, sporogonium of diskganoidal shape is pressed and born on forward part. Scattered mucus glands are present on the surface of rosette leaves, and accumulation of inorganic salts in this zone was detected. Stipules are wide and thick, covered by three-layer lamina, spinous and emerge imperfectly. They probably fix reproductive organ after discharging spores.

The shape and anatomical structure of mature gametophytes and sporophyte leaf-form of similar on dehyhrogametes stages were studied. A leave shape has changed considerably, but some characters of plastic remained. At the last level of ontogenesis these forms reflect the morphological adaptation to rain and capacity of epiphytes which use tropospheric moisture as source of water (Nina M. et al., 2004). This leaf shape predominates at rain plant of tropic zones; it has an increased ratio of length to width and hygroment of decreased quantity of pores (coming back changes), the campaing of these leaves is smooth. Configuration of leaf in shape of rosette increases the capacity of heightened humidity conditions. There is less anthropogenic activity in comparison with a chines. The oblong shape of growing campaing leads to concentric layers of phosphate deposits typical for a terra raisins. Morphology of leaf is equal to maximum watering efficiency in this climate. There are ordinary pores in price and leaves arrangement is meridional.

9.2. Morphological Variations Across Species

One encasable Psilotum species will be selected out of the catalogued delicate three taxa for observation and measurements in a dissecting scope according to the styles presented above and suggestions in Floras. The morphological variations are momentary out of its form to mind by the price of their leafy surfaces originally covered by a thin layer of cuticle. Many leafless species flowering with a natural smaller structure bring a paranoid feeling to Psilotum as a long slender finger pointing directly ahead. However, underling some stocked polygons along the upright stem traces its previous branching history. They bring a sense of hollowness for a hollow tree trunk as a shelter of myriad of insects or a hollow tooth embracing the growing beige within. All together as an unopened umbrella grasping off tiny droplet lights of the underwooded rain forest brought up the invincible stillness. Later, at the upper part, the helically enveloping scales started loosening up delicately, not at once minimizing the view but in a glorious crescendo as a herald for the coming sunny distribution climax.

The long upright part suddenly fanned out into an abrupt big angle, accenting the motionless spectacle again. The zietlike gusty moment was frozen like captured in the ancient stone wall. A surprisingly mini early Dorian colonnade circled the pedicel giving a very first impression of style reinforcement. Instantly an extreme suspension exploded, as if the giant droplet suddenly fallen due to the overcome braking of surface tenacity and metamorphosed into billions shining glittering twinkle beams dispersing to all directions. Each leaf catching a tiny pie-like parabolic ultraviolet ray, manipulated translucently by the epidermis, handed it down a level upward to the 5-15 micrometer high concentric islands buried in the convex park, glistening as mirror. The consequence is a brilliant white sun visually dazzling expose.

Cautiously looking again through narrowed eyes, one gradually detected the boundaries as the shadow made by the slope deepening outwards, compacted due its gritty nature, wearing a lilac color on top. A millennium later, the dust had dispersed by the wind, flushing down by the rain. The boundary became gradually an arch acute tenderly anticipated by 5-10 beams revealing a round 2-3 micrometer cave flatting in the center. When the dews rested above this enigmatic depression freshly bred light-orbs was generated profusively.

10. Morphological Studies and Techniques

Although comparative morphology has been extensively used in the past, they often relied upon qualitative observations. Natural variation rarely correlates with any detailed morphological description, and comparisons between taxa usually could only be effective on a broad level. Also, 2D or 3D estimates of shape would be merely open to observer biases, difficult to be replicated, and ambiguous in their anatomical interpretation compared to size. To help alleviate those problems, there have been innovative methods to capture high-dimensional morphometric data in ways that will not compromise biological information on the one hand and not introduce excessive noise on the other. Classic and recent methods to analyze morphometric data are reviewed here, both the traditional ones and modern ones for digital models like 3D pointclouds and meshes. This review illustrates the exploratory power of simple geometric methods and the avenues opened by computational geometry tools in more complex analyses. The combination of these techniques provides an effective means to study the evolutionary history of extinct morphologies from the perspective of growth and development, along with other empirical data from fields like geology. Integrating those techniques with advancements in imaging, reconstructive computation, experimental biology, and genomic tree-building will continue yielding fruitful strategies in studying morphology (E. Stanton & Reeb, 2016). The critical role that morphology ought to play in evolutionary biology – one not sufficiently reflected in granting activity and editorial practices – should be highlighted. Shape variation embodies the end product of evolution. Understanding the variations, ontogeny, growth and development, biomechanics, and environmental adaptation of shape would provide insights into how evolution works. Morphomics – the trait characterization through methods of shape or morphology – would form a weighty branch in the arsenal of current evolutionary biology. Morphometric studies of Psilotum should be well placed within the watershed of that future progress.

10.1. Microscopy Methods

Just like in other parts of the morphology of Psilotum, in the analysis of spores more than one method was used in order to corroborate the data. Different microscopy methods as plants and spores taphonomy and preservation are key facets in the fossilization of plant structures because they have exercises influencing the type of sediment that is likely to preserve a specific type of potential fossil. In addition, in palynological analysis both light microscopy (LM) and scanning electron microscopy (SEM) are often used, and the technique used will determine which features can be seen in the spores but also which features are likely to be observed in the future in the fossil record. Psilotum coloniforme spores features studied in this work are considered valuable for taxonomic determination because they are broad, being expected to be observed in the fossil record. Light microscopes also have limitations, mostly the impossibility of observing the convex sides of the spores, which also appear important for Psilotum identification. The fossil record of Psilotum is scarce; hence, there is little room for minor differences in the morphology of spores to be significant at the genus level. This consideration and that Psilotum spores are larger in specimens studied both in LM and SEM highlight the importance of SEM for Psilotum fossil record studies.

With regard to morphological terms here applied to spores in LM and SEM observations, it is worth noting that some of them are subjective, which might result in confusion. Hence, it is possible to find translated terms in the literature which modify or do not use terms employed here, although the physiognomies are the same. Chlorophyll tissues with a greater or less number of cells and sporangia with a different shape were already mentioned for different Psilotum species, in which case Psilotum is polyphyletic based on the eudedical form of the shoots and their sporangia. This polyphyly shows that modern technology with chemical or molecular techniques failed to retrieve homologies previously detected by morphological studies (Yañez et al., 2019).

10.2. Field Observation Techniques

The pantropical epiphytic "wandering mosses" genus, Campylopus, has been an enigma for over a century. The morphology of the only Central—and only continental American—species, C. schimperi, is presented in extenso, based on field and herbarium specimens. Distribution of herbarium specimens was used to present generalized pictures of ecophysiology and anatomy. A taxon's anatomy is seen as the first line of defence in evolutionary and ecological studies. This accounts for C. schimperi's radical departure from classic character states thought to be present in Campylopus. A fully aquatic growth form is advanced for all such C. schimperi.

The genus Campylopus is a pantropical epiphytic and "wandering mosses." Mosses of the family Dicranaceae have a handful of representatives among the tropical epiphytic flora, most of which are from the family Polypodiaceae. Members of the genus Campylopus are simply constructed plants and have been used for over a century for exo- and endo-phyto genetic studies. Campylopus schimperi, however, is an enigma.

Herein is presented, based on field and herbarium specimens, an extenso of the morphology of C. schimperi, the only Central—and only continental American—species of Campylopus. Distribution of herbarium specimens was used to build generalized pictures of spots and hypotheses about ecophysiology, anatomy, and divergence of this burgeoning problem. Evolutionary and ecological studies are founded on a taxon's anatomy, the first line of defence in their solutions. C. schimperi's radical departure from classic character states thought to be present in Campylopus is accounted for by this contention. A fully aquatic growth form is advanced for all such C. schimperi.

Likewise, although tropics, ecology, geography and anatomy of C. schimperi must be viewed from a wider vantage point, one more mindful of patch and individual object vicariants—things that can be tinkered with and "engineered" to perpetuate growth forms, evolutions, and distributions in epiphytic and non-epiphytic plant communities.

11. Applications of Morphological Research

While most studies of the plant morphology have focused on vascular plants, there is also an important and diverse amount of research to be done on non-vascular plants. Living thalloid non-vascular plant groups such as hornworts and liverworts are not only of ecological interest but also offer possibilities of studying convergent morphological evolution and plastid evolution. As they typically lack the conventional life history characters useful for constructing cladograms, geometry-based shape comparison offers a way around character broadness problems. Bryophytes acquired phylogenetically new morphologies such as the moss sporophyte and the liverwort perianth whose disparity of form exceeds even that of flowering plants. Non-water conducting cells are of mechanical versus water transport importance. For the origin of stomata, guard cells of liverworts contrast with those of moss sporophytes and hornworts, with genetic candidates for stomatogenesis being identified by sequencing the hornwort genome. Their armoured vegetative spores have been histologically studied as preserves for deciphering macroevolutionary patterns in paleoecology and climate change (E. Stanton & Reeb, 2016).

A plethora of morphometric studies and applications exist to establish the phylogenetic significance of moss and liverwort traits at various scales. Available published options may be manipulated subsequently for finer phylogenetic studies and also potentially updated with a higher resolution topology, new taxa, new 3-D morphometric techniques, and new results from cladistically more tractable groups (Bucksch et al., 2017). Other ongoing studies are comparing 3-D footprint casts of fossil mosses to modeled HTM spores for identification and distribution mapping. Studies of characters 2-D morphometrics with phylogenetic significance include more general visually defined traits such as capsule shape, ornamentation, conico-cylindric leaf shape, large versus small cell morphologies, germ teeth, and tooth morphology than simply tooth number. Building into regional databases through a compilation of up to 25 prior DNA studies combining plastid and nuclear markers is also under way. In tandem is a geographic biomass and mining zones database to document observed and potential population declines as the basis of conservation prioritisation and management.

11.1. Conservation Efforts

Plants continuously interact with their surrounding environment. They possess a myriad of adaptations in form and function that allow them to cope with the challenges of terrestrial existence. The biological study of these adaptations—plant morphology—has long been a principal pursuit of botanists. Integrated approaches to the study of plant morphology offer a means to understand both the evolution and development of terrestrial plants as well as insights into plant responses to environmental changes.

The application of the extensive literature regarding the anatomy of Psilotum to the issue of the conservation of this endangered plant has been relatively straightforward. Many of the extensive data sets on morphology, anatomy, and tracheid diameters have been used to describe the status of the Florida populations of Psilotum, to consider the global issues related to the uniqueness of Psilotum, and to make recommendations for future restoration work in Florida.

The initial suggestions made to conservationists concerning the basic ecology of Psilotum were followed closely. The sites of the remaining Florida populations remained undisclosed. Efforts were immediately made to protect and fence these sites from human and mechanical disturbances. It is doubtful that the populations could have persisted without these initial, straightforward considerations. The sites were chosen primarily on the basis of the presence of a parental tree plant of 5 to 8 cm dbh and a maximum canopy closure of 50% in areas covered with saw palmettos. These sites were by no means selections for uniqueness but merely the “best of the worst.” The initial idea was that fenced sites protected from the chain-sawing of parent plants should be free from disturbances for two years. However, despite 14 years of protection, the sites remain fragile and require regular visits, raising the question of how long even these narrow sites can be preserved in an urban environment.

Although it was not possible to impose a model for comparisons of all sites worldwide that could be fit to include Psilotum, some initial steps in this direction appeared tractable. In Florida, all remaining sites are now known and monitored. It seems likely that such efforts can point to progress elsewhere.

11.2. Biotechnological Applications

Hormones present in renewable plant extracts are widely used in agriculture to control plant growth and development. Moreover, they are employed for seed germination, rooting of cuttings, leaf senescence, mildew treatments, or to stimulate protein production in plant tissue cultures. Finally for condensation of flowering in flower crops such as orchids. The use of synthetic hormones is also explored in this respect, especially the commercial products. Likewise, their effects on seedlings growth, root elongation and shoots formation of different species is pointed out.

Plants response to biotic and abiotic stress by inducing defence and repair mechanisms. Plant viruses, bacteria, fungus and infeasible fungi are agents mechanical damage that can lead to cellular leaks or tear. Causes of.

Arbuscular mycorrhizal fungi are important mutualistic symbionts of land plants. Beneficial effects on plants and stimulant effects on root growth are shown in non-mycorrhizal sponge plants, monocots and dicots such as tobacco, barley, ferns or pines. Induction of root branching or localised elongation as the basis for colonisation. Developmental plasticity which shifts the growth pattern of the root from a forward to a lateral direction. Depending on plant age and fungal species, ecophysiological traits are correlated with different types of root branching.

Actively expressed tubulin-based cytoskeletal structure is essential for asymmetric and polar growth of specialized cells in land plants. Induction and turnover are intimately associated with the coordination of growth, morphogenetic changes and the maintenance of daughter cells in determinate tissues. The exclusive evolution of highly elevated and complex morphology, which necessitated diverse new structural and developmental features and mechanisms, is critically dependent on the establishment of a cytoskeletal architecture appropriate for the generation of varied morphologies.

12. Future Directions in Morphological Research

Morphological development and the evolution of morphology in plants it is a spur to educational reforms all over at least the Southern Con- tinuent (E. Stanton & Reeb, 2016). Teaching drawings and unlabeled cross- sections are vehicles of awareness that north-west European area educational programs agonise to create. Study of morphology and drawing are removed from basic understanding of plant forms and functions. Cross-sections are not recorded and the rendered flesh often takes on a life of its own devoid of intellectual control as stalking columns masquerade as cells. It seems the twilight of the 20th Century is a time of ferment in the field. Views that anatomy is the unifying theory of plant form are under siege. These views were comprehensive and rigorous. In morphogenetic terms meristems, whole plants and plants as plant cultures are births and their temporal morphologies. Mortuary topologies, petrifactions, destruction of culture and premature death are then cast in preserving schemes as an eternal guarantee. Four-line generative rules resulting in L-systems allocate non-specific position to these developmental schemes. Further, Scherer's exhaustive treatment assigned complex threedimensional growth as a set of parcelled manipulations but analysing external morphology through a recast of 2-dimensional paper folding was more understandable. The difficulty in achieving appreciation of such material 35-45CM children by way of grammatical plastic hors d'oeuvres was tragically demonstrated by Evans-Freke's experiment. Such was the plastic-artistic approach pre '1985'. Morphometric studies tend to be largely of surface ornamentation. Nevertheless, surface textures are a rich source of taxon and relationship identifying characters. The first job to be tackled would be the development of a robust database for gathering with sophisticated output options due to the sheer amount of time required for processing. Emphasis to be placed on 3D geometries or aspects and the orthography of occurrence and shape variation in order to determine and consolidate area distinctions etched in a band of texture.

12.1. Emerging Technologies

Since the discovery of transcribing and translating pathways, replete with ribosomes churning out proteins and the ability of a spatially-distributed set of nanomachines (the proteome) to self-organize and reassemble into new structures (the morphome), all under genomic control, and to do it with precision and error correction, it was clear that affordance, in the semiotic sense, could not be more widespread, spanning scales from the atomic to the geological. These pathways rule from within a hierarchy of levels that can be carved out in the abundance of categories in which it plays out. But as spellbinding as it was and continues to be to peek into the hidden world of living processes, it is not the sole significant question to ponder. An equally and arguably far more profound exploration emerges when peering into the unseen constraints, or shadows, molding those pathways, styles of life, or morphemes—metaphorically speaking margins that craft the living formats on which processes can impose their temporality (P. Lemoi, 2012).

The inheritance of styles of life might be far more ancient than that of patterns of the living world. The parsimonious emergence of organic forms in spatial continuous time might have predated their ‘solidification’ by molecular morphogenesis, quite possibly explaining the dizzying richness of prebiotic body plans. But inexorably constraints of materiality, expressive localities, and chaotic complexity kicked in (in relational terms) in a turbulent compaction of the primordial world, expanding and fortifying the dimensions of the artificial ‘morphome’ (broadly speaking of formats across the continuum) and establishing possibilities for control that surpassed the fitness time.

Information imbalance could further stretch the gap: while the emergence of life was an incursion into morphospace, the ensuing discrete states of the sort celebrated in a ‘cathedral of structuredness’ may be neoteric transient settlements in a topographically far more complex continuous morphospace that has never ceased being explored. It is surmised that the exploitation of knowledge in the form of accumulated preferences and priorities for vantage patterns and fixed formats—that is, habits—turned out to be nothing short of a revolution in signification that completely transformed the production of bodies, lifestyles, and the world.

12.2. Interdisciplinary Approaches

The evolution of morphology can be studied by investigating the inter-relationships between gross and fine structure, but progress is constrained when investigated with a single discipline. Each discipline uses its own methodologies, terminology and approaches to classify morphology, restricting cross-disciplinary communication. It is visualised how the structure of the branch systems of Psilotum, a vascular plant, can be more easily understood by separating insights from geometry, morphometrics, histology, anatomy and development than by a traditional integrated description.

In recent years, there has been a growing appreciation for the ways in which evolutionary biology can benefit from interdisciplinary collaboration with other fields such as mathematics, computer science and physics. Quantitative and computationally intensive methods developed in other fields have the potential to enhance, modify or extend the scope of traditional methods in evolutionary biology (E. Stanton & Reeb, 2016). Conversely, the enormous variety of morphological forms across all branches of the Tree of Life and how they arose is likely to inspire and inform new ideas in other disciplines, allowing them to advance creatively in ways they might not otherwise achieve. Examples of this inter-disciplinary interaction are provided from the study of a simple but ecologically and evolutionarily significant vascular plant, Psilotum nudum.

13. Case Studies in Psilotum Morphology

The second fern family to be examined is the Psilotaceae, which has played a historic role in the study of morphology due to the long discussion surrounding the status of its two genera, Psilotum and Tmesipteris, the anomalous nature of which led some to deny them true fern status, placing them in a separate group "Psilotinae". Psilotum is among the most unusual of plants possessing true leaves, and it has frequently been cited as an example of a simple plant which can lend insight into the evolution. However, morphological study of Psilotum today is almost non-existent, notwithstanding elegant palynological work. To some it may seem too simple to be worth serious consideration — but it remains part of the fern world just the same, and evidence suggests that there is more than enough complexity concealed beneath this exterior simplicity to keep many busy for some time to come (Yañez et al., 2019). The Psilotaceae were known from the earliest fossil spores, dated about 410 million years old, and timely cyclostome shoots similar to Tmesipteris have been described from deposits as old as the late Upper Cretaceous. The family is well represented in the fossil record since this time, but in many regions modern aerial systems in which the arrangement of lateral branches is palmate, in the form of a whorl of branches, are common. A western North American species (Psilotum triquetrum) even appears to retain an ancestral condition whereby the sporangia are borne on a terminal fork in one of the dichotomies of the branch instead of being borne in clusters, as in all of the other extant representatives. All extant species are epiphytic, and occur in shady, humid nooks of rocks or tree branches. In appearance, representative species (notably P. nudum) are straight, slender, simple or clustered, green twigs of the same general character as the spore-bearing stele of the filmy fern Hymenophyllum.

13.1. Regional Variants

The species Psilotum contains two morphologically and ecologically distinct varieties: the tropical rainforest-dwelling Psilotum nudum and the pteridophile Psilotum complanatum, a true epiphyte. These realities are reflected in subtle but definitive differences in form and development. The general structure of two varieties is similar: a long, slender, erect or suberect stem, branched, with pale green, leafless, cylindrical stems. Ascending stems are much shorter, closely appressed to the substrate, with a few segments and attenuate in substantially exilis-spored forms. Generally, there are no tracheids, with the distinctive anatomical characteristics including lignified thicker-walled cells imparting toughness. In making orientation determinations of the strobilus, traditional morphology is supplemented by explicit regard for development. Beyond the recognition of these forms, further morphological resolution is necessary. Thus, while the spinose spur of the epiphytic species is abundantly branched, leading to a reduced, rounded vegetative tip or head, that of the terrestrial species, which spirally reminisces its distally diminishing segment pattern, is of unbranched, subequal spurs, there being outside these basic characters additional features of two adjoining to which differing adjacent sectors are added. These details of structure have been discovered through persistent search for indubitable differences between adjacent forms to the general detriment of direct knowledge of the species. They have left effect of terminology to express them, crumbs desperately converted to hoofprints in a word-search through the fields of botany, morphology, and astronomy.

However, the indices hereafter are arbitrary. Upon taking crabs, the delay in fertilization is about fourteen after the first; spores of dry sporanges burst around this time as fali at obliquity or the roll of the lip, fuged filament, transferring needles. All formed nigra and are collected over the immediate vicinity, filtered from debris and diluted in the water where they are to remain. Approximately one hundred scrambled scraps are introduced. A few periods of total darkness follow on six occasions within the next few cycles despite a visual paucity of the first egg cases. It is presumed that an abundance of sapling generation at the surface indicates poor gametophyte development.

13.2. Specific Environmental Impacts

By virtue of both anatomy and ecology, Psilotum is independently positioned among the living vascular land plants. Its neither root, leaf, nor wood features make it a challenge for investigation of their paleobiology. More ancient plants than leafy euphyllophytes had lived some 400 million years ago. Such plants had acquired aboveground means of competing discounting height advantage and thus light competition by developing massive networks of filiform shapes, similar to modern swamp. Until recently, Psilotum remained unconsidered by the mainstream in paleobiology. Recent advances in mega-fossil discovery in the Lower Devonian strata, however, revealed vestiges of ‘leafless-land’ in the hollow trunk. Such prior-to-leaf-strobilus duality leaves acts earlier than leaf-whorled strobilus and leaves itself to a more straightforward matter of investigation.

Among the living vascular land plants, the whisk fern (Psilotum) has received the most interest regarding the shift of form between dichotomously branched, leafless vegetative shoots, and branched axis, where leaf-strobilus, and a spool profiles were acquired independently. The leafless axes are made up of cylindrical, closely packed H-shaped rod-like of a split module. Here, it gradually moves into a two-dimension circular sheath with thin walls and wide lumen where it transforms into a leaf beneath a strobilus. The transition from axis to leaf was proposed as one of two categories of axial flattening, which is independent of foliage. During this transformation, the stem profile changes from circular in the axial dichotomies to sheath profiles. Each sheath is made of both layered and structures. Combining the two categories of arranged fibrils into polar and axial sheets would allow thickness-dependent morphologies.

There are three specialized bifunctionalities in leaf-blade and leaf-sheath. But any trace is lost in the ultimate leaf-like strobilus in either growth forms. Early divergences in leaf-strobilus absence numbers were found among taxon-particular on sampling. All polysiphonic Leptosporangiate ferns and polystichaceous fossil record information is insufficient. Further conductor reduction in the mature free leaf-strobilus was derived. This is done by lowering the water pump and facilitating free fruit dissemination. Ultimately, leaf, habit, and fruit were created through the foregoing radical reconstructions. Finally, the classic leaf-strobilus handling, and were tightly enclosed among.

14. Challenges in Morphological Research

Beyond the historical importance of the morphogenetic model plant Psilotum nudum, this genus serves as the last extant representative of the once-thriving whisk fern lineage. Placing it in the context of the fern tree of life, however, remains challenging. Unlike other vascular plant lineages, the mechanism and developmental basis underlying the switch of forking growth in appendage generation in leptosporangiate ferns is poorly understood. Gravitropic and hydrotropic lateral movements of developmentally active meristematic tissues in basal tuberous monopodial Psilotum branches provide a model system to study the evolution of modularity, shedding light on the origin and diversification of the fern life cycle. Additionally, contrary to the long-standing view of rhizomes, stipes, and filmy leaves as differentiated axial-leaf units, direct observations via 3D micro-computed tomography show that the vegetative morphologies of the terrestrial fern Psilotum are similar to those of the aquatic liverwort Ricciocarpos. Tiny foliar shapes in three-dimensional arrangements generate dual structures to sequester sunlight above the water surface for photosynthesis and to siphon water and nutrients from drip flow to control cellular hydration below the surface. Understanding the environmental transitions of this ancient lineage of the plant kingdom may aid the control over spreading pteridophyte ferns in modern wetlands. Morphological transformations can be the result of structural adaptations that allow organisms to overcome particular environmental challenges, or to exploit different niches. Understanding whether morphological divergence occurs as adaptive evolution or a result of plasticity is ambiguous.

Development is increasingly recognized as a process that unfolds over time and is often sensitive to external conditions (plasticity). Despite their importance, phenotypic plasticity and adaptive evolution are often studied separately. As a result, while some partially connected traits may evolve in parallel, there is little understanding of how development can constrain or facilitate this process. Reconstructing the evolution of the morphologies of poorly explained groups, such as the enigmatic Vendobionta, provides an opportunity to clarify the connections between plasticity, adaptation, and development because they have poorly or totally unexplained growth patterns and histories. Vendobiontan morphology has traditionally been studied from the standpoint of evolutionary interpretation. Although there has been considerable innovation in techniques to study the tri-dimensionality and growth patterns of fossils, as well as in how the Darwinian paradigm applies and should be modified for an explanation of extinct groups, the biological affinity of these organisms remains the subject of debate (B Meyer, 2009).

14.1. Data Collection Issues

New World plants of the genus Psilotum ('whisk ferns'), particularly P. nudum, share recent above-ground morphological adaptation to light-rich terrestrial environments with several other New World ferns. Synchronized changes in above-ground morphology were observed and documented digitally in colonies of P. nudum transferring from deep shade to sunshine. As this change took place, elongation of aerial stem and branches was observed to increase rapidly, triggering the elongation of dichotomies in the apical region a few air-days later, simultaneously as the dormancies of various applications prior. Indirect effects of light (e.g. temperature) or other environmental variations were systematically ruled out as natural triggers, and experimentation documented that growth responses were rapid enough to be safely explained by sensing of a light change. Many of these were not predicted at the initial analysis, including in plants grown in isolation and therefore not by any direct effects of the plants sharing sunlight. Examinations of leaf-strategy confirmed that applications in this fern colony were predominantly second and third type. Mass-aggregation of the live spore yield has been digitally documented for spore packets that become buoyant within about eleven minutes in humid air and suffering less than 4% hint no-spore loss. Colony growths in observation trays have been documented beyond the twenty-fifth generation for initial plants logged early on in this long-term research program. These efforts with Psilotum address the need for biologists to document both with highly sophisticated equipment able to gather quantitative data and with the creativity, artistry and persistence seen for the biophysical data concerning moss morphology and organelle motility. This chapter summarizes data collection for morphology and mild measurement systems for growth observations, reviewing them in conjunction with recently-published data.

Since studies began on aspects of Psilotum nudum, further overhead air-filled stems could be detected reinforcing crown morphology ( (P. Lemoi, 2012) ). Recent capture of observations of a natural concerted response in colony growth pattern to a change in sunlight raised the focus on these plants' long hydroponic strands with ornamental fronds for other types of morphological data acquisition. Improvements to measurement considerations equipment generally satisfactory for biophysical data measurements were attempted with Psilotum chronicle detailed observations of morphology and orgiway that were gathered to frame it within quantitative developmental biology. Without use of high-powered projectors, it is hoped that this more common photographic documentation provides a useful counterpoint and alternative opportunity for creativity and artistry in data collection.

14.2. Interpretative Difficulties

Nevertheless, these are not the only difficulties that the problem of eternal morphology of Psilotum presents. From a more general point of view, its tortuous history constitutes a cautionary example on schemes that, relying on morphology, try to display a coherent phylogeny connecting diverse taxa. The hypothesis of a close relationship between vascular plants and Psilotum is the most elaborate and complex one, based on a very small number of cryptic morphological features. Other schemes are simpler. For example, apparently at some time it was proposed that Psilotum was a homosporous horsetail having enveloping leaves. This scheme had the merit of maximum simplicity, but also the strong demerit of an exceedingly superficial understanding of the complex nature of Psilotum and of the correct morphological homologies. In compositional terms, it is simple but poor. The best hypothesis in morphologic terms, however, is decidedly poor in compositional terms. This imbalance provoked further struggles of militant botanists between time-honoured teams and the formation of a close phylogenetic relationship between cordaitean pteridophytes, probably to discuss about the problematic actinosteli in the former, and the attempted explanation of anatomical features by repeated units. One of the reasons that some plant groups underwent a long discussion of their appropriate phylogenetic placement and that others, although differently problematic, passed to put their placement beyond doubt, is obviously to be found in their effective worldwide occurrence and diversiculativeness. This is the reason why, perhaps because of involvement of economic concerns, so many ministers of social policy for education tried to bring keepers, nasty creatures set on force exorbitant demands on apparent education. No such unreasonable policy has hitherto been applied to Psilotum, perhaps because little parties care about it. The disinterest of many biologists explains why many puzzles of Psilotum’s morphology were persisting for decades, whereas presently perplexing problems of other groups have often been resolved in a few years, either by generation of missing deciders or by a new point of view.

15. Summary of Key Findings

This revision finds Psilotum nudum, Rammelsbergia sp., Tmesipteris lanceolata, and Psilotum triquetrum in the Psilotaceae clade and a clade containing only Equisetum species. Analyses with this revised taxon set yielded trees with the same topology as those of the earlier analyses. Beyond these modifications the results were similar, as evidenced by the strong support for coalescent branch length estimation of the Psilotaceae and Equisetaceae, even with the Planorbis sample excluded. The addition of more Equisetum representatives will likely assist in resolving relationships within the Equisetaceae. A sister relationship between Psilotaceae and Equisetaceae has been reported previously (G Karol et al., 2010) on the basis of setologically based studies. This study represents another independent approach to addressing such relationships. All phylogenetic analyses reveal a very well supported clade that includes the marsh ferns of the family Ophioglossaceae and the horsetails of the Equisetaceae. Material failing to represent the Psilotaceae and Equisetaceae clades was relatively rare and consisted entirely of isolated branches.

16. Future Research Opportunities

In the past years, we investigated the evolutionary morphology of Psilotum nudum incorporating 3D imaging-simulation methods. We first demonstrated the differences in morphological astronomical characteristics of branching of the shoot and rhizome between three species of Psilotum (P. nudum, P. triquetrum, and P. complanatum) using two-dimensional analyses on shoot and rhizome x-rays taken by a lab-built synchrotron X-ray phase-contrast microtomography system (D'Ario et al., 2024). In addition, we showed the mathematical regulations in the vertical growth of the rhizome of P. nudum and its evolutionary novelty using a discrete-continuous hybrid model of the fractal tree. Moreover, we tested the unaddressed origination of the great morphological diversity of the shoots of Psilotum and re-evaluated the hitherto hypothesized evolutionary relationships among Psilotum species using a multi-scale x-ray imaging system and a particle system simulation. Due to the simplicity of the organography and homologous arrangement between species of Psilotum, this plant group is a great system for investigating morphological diversity. Furthermore, for a better understanding of the botanical research, even broader mathematical instruments can be utilized. For example, the functions of the bloom in flowers among angiosperms greatly differ between species, and the mathematical models are relatively few considering systemic morphological similarity between species. Therefore, this plant group may also be a great target for further observations.

17. Conclusion

This work discusses the nature of Psilotum, a primitive vascular plant, on the basis of the relationship between Nyctanthes arbor-tristis and Mimosa pudica as fuzzy sets. The fuzzy transformation logic is created to process the varied attributes of the biophysical feature similarities for Nyctanthes arbor-tristis and Mimosa pudica. In the meantime, an integrated event architecture is implemented to discover the fuzzy nature in the biological community for atmospheric fine particular matter from a logical point of view. Several approaches are explored to process the display of fuzzy transformation logic, and multiple methods are applied to provide an environment to develop the fuzzy transformation logic on a platform.

One advantage of fuzzy set theory concerns its acceptance of uncertainty and vagueness of information and grading of events. Finally, the event architectures show relationships among thunderstorm, ozone, and fine particulate matter via fuzzy-based scalability and proximity measures. A subsequent contest is ancient knowledge in the comparison of African Baobab and Asian Banyan trees, which are highly ubiquitous in Africa and Asia, respectively. Future applications of this work include learning features of fuzzy transformation logic for other biological communities, such as the comparison between conifer and broadleaf trees in mapping fire incident distributions in different regions, and ecosystem gross primary productivity outputs. It is also desirable to explore the estimating ability of various fuzzy membership functions and fuzzy operators in the fuzzy transformation logic.

The understanding of the studies of fossilized specimens of a species is also desired. Intensive observations of paleobotanical collections such as fossilized remains of Psilotum will answer these basic questions: To what extent are this work’s observations and interpretations sufficient? To what extent are there limitations or weaknesses? What new items need to be included? A thorough investigation will undoubtedly point out the directions of future research and application of fuzzy set theory in biological community studies.