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Terrestrial homosporous fern-like plants. Stems jointed, rush-like, sometimes hollow; subterranean stems with numerous wiry roots; aerial stems green; internodes commonly ridged longitudinally, with stomata in rows or bands in the grooves and with ridges bearing siliceous tubercles or bands. Leaves small, each with a single nerve, whorled and joined in a sheath. Strobili terminal on vegetative shoots or, sometimes, on branches or specialised shoots lacking chlorophyll, bearing stalked peltate sporangiophores, with sporangia. Spores chlorophyllous, spherical with 4 elaters. Gametophyte green, epigeal, thallose, irregularly strap-like, branched.
Terrestrial plants. Aerial stems erect, uniform or of two kinds, fertile and sterile, hollow, ribbed; arising from creeping subterranean, often very deep, rhizomes; producing whorls of branches at the nodes; some species produce tubers borne singly or in rows like strings of beads, from the rhizomes near the roots. Leaves reduced, in whorls, those of each whorl being united to form a sheath around the stem at each node
Plants with jointed stems, with distinct nodes. Leaves small, whorled, fused into sheaths; tips remaining free, toothlike. Sporangia borne on peltate sporophylls aggregated in cones 0.3--10 cm. Spores green (except white in hybrids), all 1 kind. Gametophytes green, terrestrial, unisexual; male gametophytes smaller than female.
Aerial stems erect, hollow, ribbed, arising from creeping subterranean rhizomatous stems and producing whorls of branches at the nodes
Leaves reduced to a many-toothed short sheath at each node
