A family of the Pteridophyta in the wide sense, or of the Lycopsida in the narrower sense, of plants similar to the clubmosses (Lycopodiaceae), but showing heterospory, with megasporangia, each containing usually only 4 large megaspores (which germinate into female gametophytes), and microsporangia, each containing many tiny microspores (which germinate into male gametophytes). The plants have tiny leaves, like the true clubmosses, but these may be either spirally arranged and all of similar form, or in 4 ranks along the stems, 2 ranks of leaves being much larger than the others. All Selaginella leaves have a tiny, tongue-like structure, the ligule, on the upper surface near the base. All the species have their sporangia in cones. Probable relatives of the living Selaginellaceae were very important components of the Upper Carboniferous coal-measure forests (Lepidodendrales), and many were large trees. There is 1 genus (Selaginella), with some 700 species, of world-wide range.
Subjects: Plant Sciences and Forestry.