Pteridophyte: Introduction

 

Introduction to Pteridophytes

Pteridophytes or ferns are a group of vascular plants with well-developed roots, stems, and leaves, or more usually, fronds, which reproduce via spores and have neither seeds nor flowers. True ferns are the largest group of pteridophytes, although the term is sometimes used to cover all the members of the clade.

Accounting for around 10,600 species, they occur in a variety of habitats, particularly in warmer areas, and many have ornamental or agricultural uses such as the maile, a Hawaiian form used in decorations. The pteridophytes depend on a constant supply of water for the maturation of the spores. Most of them require shade for germination, initial development, and rooting. Though atmospheric humidity is advantageous, too much of it becomes detrimental for their growth. Their reproductive habits and the physiochemical nature of life, sap, or juices make them peculiarly vulnerable to drought or desiccation. They take years to produce young plants of good size and many dry up without ever having produced sporangia.

Pteridophytes will sensibly divide into two groups-the microphyllous and the megaphyllous. The former sprouts in wet, shady places and grow up to a foot. Their leaves are small, broad, and thin. Some of them are terrestrial while others are aquatic. The megaphyllous Pteridophytes that usually grow in gardens, hedges, or similar places are the real fern. They have thick, fleshy, and smooth fronds with deeper lobes which often branch again. As a result, these fronds grow large and may exceed 15 feet above the ground whose lower ones emerging from the centre force those above to spread outwards and become upright and erect plume or elate, thus forming a fountain-shaped crown. When old, these fronds die but remain hanging on the tree. Very often the margins of the leaves are black and serrate or finely sub serrated. The function of a leaf is to create climate in a hot country by blacking off heat. The oldest fronds die and may even drop, if they do so the fresh leaves will retain the water supply better because of increased humidity owing to lack of sun heat and consequent quick evaporation. The mesophytic condition rises to a higher grade wherever its growth is freely stimulated by the influence of shade and keeping permanent moisture about its engines of disintegration. The broad and toothed fronds of fern retain the carbonaceous products of its food; and in some species the foliage is peculiarly arranged in a spiral manner.