Small leafy plants, terrestrial or rooted in mud. Stem branching or short and corm-like. Spore-cases solitary, axillary or borne on the upper surface of the leaf at its base and enwrapped in its margins. Spores of two kinds, the large ones (macrospores) developing prothallia which bear archegonia only, and the small ones (microspores) giving rise to antheridia only.
1. Selaginel'la. Terrestrial. Stem slender. Leaves small. Sporecases very small, axillary, some containing the orange-coloured powdery microspores, and others with 3 or 4 larger macrospores.
2. Iso'etes. Growing in water. Stem corm-like. Leaves elongated and rush-like. Spore-cases large, enwrapped by the spreading bases of the leaves.
S. rupes'tris, Springi A little moss-like evergreen, growing on exposed rocks in dense tufts 1-3 inches high. Leaves awl-shaped, with a grooved keel, and tipped with a bristle. Spikes 4-cornered.
I. echinos'pora, Durieu, var. Braun'ii, Engelm. (Quillwort.) A small aquatic grass-like plant with a corm-like stem, bearing 15-30 slender leaves. The large sporangia axillary, partly enwrapped by the thin edges of the excavated bases of the leaves, beset with small spinules. - Lakes and ponds, chiefly eastward.