Affinities of Anthoceros with other members.

Affinities of Anthoceros with other members.

Anthoceros shows affinity with algae, members of Hepticopsida and Bryopsida of Bryophyta and Pteridophyta.The affinity and relationship of Anthoceros with green algae lies in the presence of a single large chloroplast together with a pyrenoid in cach cell of the gametophyte and in the formation of biciliated sperms. Anthoceros shows affinity with members of Hepaticopsida such as Riccia, Marchantia, etc. in the construction and structure of sex organs and in the apical growth of the thallus.It has affinity with members of Bryopsida i.e. Polytrichum, in the structure such as presence of columella, reduction of sporogenous tissue etc. and

development of sporogonium. The spore production from amphithecium

resembles the condition of that in Sphagnum. Anthoceros also shows sunken

archegonium and development of antheridium from hypodermal initial cell

like Pteridophyta. Highly developed sporophyte having photosynthetic tissue,

functional stomata, intermediate growth etc. indicate that anthoceros

sporophyte is on the way to be a nutritionally independent structure which

shows a close affinity with the members of Pteridophyta.

1. Affinity with the Chlorophyceae: The features which Anthoceros

shares with the Chlorophyceae are :

(1) The smaller number of cell but larger size and definite shape of the

chloroplasts.

(2) The presence of pyrenoids which are characteristic of cells of green

algae only. The pyrenoids of Anthoceros and green algae function similarly

and form starch grains at their periphery.

(3) Simple, green, dorsiventrally flattened thallus-like plant body and its

branching.

(4) Biflagellate sperms with both flagella of whiplash type.

The above mentioned features of Anthoceros which recall those of the

green algae are considered by some to indicate that Anthoceros stands close

to the line of evolution leading from the green algae to the land plants.

II. Affinity with the Liverworts: The features which are common with

the Liverworts are as follows:

(1) A simple, thallus-like gametophyte without any differentiation of

tissues and absence of any appendages, except the smooth-walled rhizoids

are the features which Anthoceros shares with the Metzgeriales such as

pellia.

(2) The similar apical growth of the thallus lobes.

(3) The sex organs differ in essential details but are constructed on the

hepatic plan and the biflagellate sperms similar to those of the Hepaticae.

(4) The construction of the deeply emarginate growing point as in the

Marchantiaceae.

(5) The separation of the amphithecium and endothecium by periclinal

walls in the same way as in the Hepaticae.

(6) The differentiation of archesporium into spore mother cells and the

elongated sterile cells which develop into pseudo-elaters. In the related genus

Megaceros the walls of the sterile cells are spirally thickened to form elaters

as in the Hepaticae.

III. Affinity with the Mosses: The features that are common with the

mosses are the following:

(1) Development of a highly diffferentiated, ventilated photosynthetic

system in the capsule wall.

(2) Presence of a central solid core of sterile cells known as columella

which is entirely endothecial in origin which shows Anthoceros resembles

Sphagnum.

(3) Archesporium greatly reduced forming a small part of the capsule,

(4) Archesporium differentiated from the inner side of the amphithecium

and dome shaped that covers the top of the columella as in the Sphagnum

moss.

IV. Affinity with the Pteridophytes: The features in which Anthoceros

resembles the pteridophytes are the following:

(1) General similarity in the thallus structure of Anthoceros and the fern

prothallus.

(2) Sex organs as in pteridophytes are deeply sunk in the gametophyte.

(3) Similarity in the structure of the mature archegonia.

(4) Campbell holds that the elaborate, semi-parasitic sporophyte of

Anthoceros with its typically ventilated assimilatory system and continued

growth denotes the nearest alliance to the independent rootless. leafless

dichotomously branched sporophyte of the primitive fossil vascular plants,

known as Psilophytales.

Discussion:

Thus studying the above features regarding affinity of

Anthoceros with members, it is justified the contention that Anthoceros is a

synthetic type. It forms a connecting link between the Liverworts and the

Mosses on one hand and links the bryophytes with the primitive

pteridophytes on the other. It is also indicated a remote connection with the

Chlorophyceae.

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