The plant of Selaginella is sporophyte and is evergreen, delicate herb with adventitious roots. The plants are diverse in form. In some species the branching stem is prostrate growing along the surface of the ground or may be suberect or may be scandent.
The stem is covered with four rows of small leaves, out of these, two rows are of smaller leaves and two rows are of large leaves. Species with dimorphic leaves such as S. kraussiana, S. helvetica are grouped in the sub genus Heterophyllum. In other species of Selaginella, the stem may be erect with a spreading mass of foliage leaves uniform in size, such species like S. oregana, S. spinulosa are grouped in the sub-genus Homoeophyllum.
The stem, covered with these green leaves present a moss like appearance, hence the plant is called little club moss. The leaves are in pairs and are conspicuously different in size. The small leaf of each pair is inserted on dorsal side of the stem and the larger on the ventral side.
Successive pairs of leaves are so arranged that large leaf alternates with a large leaf and small leaf with a small leaf. The leaves are always narrowly triangular and pointed. They are liguate, in that they bear a flap like out-growth at the base called the ligule (Latin, ligule = little tongue). The leaves are simple, lanceolate or ovate in form. Usually they are thin and delicate except those of xerophytic species.
ADVERTISEMENTS:
At the place of bifurcation of stem, a leafless, colourless, elongated cylindrical structure grows downwards. This was called ‘Rhizophore’ by Nageli, and is quite different from the root in that it has no root cap. Rhizophores are unknown in 5. cuspidata. Rhizophores typically develops tufts of adventitious roots at its apex.
The main plant body of Dryopteris is also a sporophyte and is differentiated into root, stem and leaves. The stem is a rhizome which grows obliquly under the surface of soil, only the apical portion coming out of the soil surface. The old portion of rhizome is covered by brown hairy structure called rementa.
From the upper surface of rhizome arise large number of leaves from 25 cms to 1 metre in length. These leaves are bipinnately compound. There are two rows of pinnae on the rachis, each pinna redivided into pinnules. Rachis is also covered over with ramenta. Leaves show circinate vernation (i.e. coiled like a spring) when young. The gametophyte of fern is called prothallus which bears archegonia and antheridia and rhizoids.