The World Flora Online

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.

Plantes terrestres, tout au plus palustres.\n\t\t\t\n\t\t\t\t Sporophytes': 2 n, herbacés, vivaces, rhizomateux; faisceaux collatéraux, fermés.'Feuilles'verticillées, petites, squamiformes, indivises, uninervées, celles d'un même verticille unies à la base en une gaine entourant la tige ou le rameau et terminée par des lobes ou des dents ; base de la gaine foliaire éventuellement transpercée par les rameaux axillaires.'Sporophylles (= clypéoles) en verticilles groupés en strobiles au sommet des tiges ou des rameaux.\n\t\t\t\n\t\t\t\t Spores toutes semblables.\n\t\t\t\n\t\t\t\t Gamétophytes : n, le plus souvent unisexués, épigés, verts, rubanés-aplatis, souvent un peu ramifiés-digités, les femelles plus volumineux que les mâles, tous fixés au sol par des rhizoïdes ventraux 1-cellulaires; anthéridies donnant des anthérozoïdes gros, à cils multiples.\n\t\t\tFamille actuellement monogénérique, existant dès le Carbonifère inférieur.

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 Leaves reduced to a many-toothed short sheath at each node

Plants without secondary thickening; ribs of the stem offset at the nodes; stem ordinarily with a large central cavity and two additional sets of longitudinal cavities; the vallecular cavities, which traverse the cortex beneath the grooves of the stem, and the small carinal cavities, which are adjacent and internal to the vascular bundles (on alternate radii with the vallecular cavities); stomates in regular longitudinal bands in the grooves of the stem; lvs small, scale-like, often not photosynthetic, connate to form a sheath at each node, each lf continuous with a ridge of the internode below; [Equisetaceae] branches, if present, usually whorled, alternating with the lvs, arising from small superficial primordia at the nodes and breaking through the base of the sheath; sporangiophores peltate, each with 5–10 elongate sporangia under a polygonal cap; spores each with 4 spirally wound bands (elaters) with enlarged tip; sperms multiflagellate.

Plants perennial, homosporous, small to large, terrestrial, aquatic, or in shallow water. Rhizome creeping, sometimes erect or ascending, blackish brown, branched, with nodes; nodes with roots densely covered with trichomes or glabrous. Aerial stems annual or perennial, erect, monomorphic or dimorphic, green but lower nodes often blackish brown, terete, with nodes, hollow and with longitudinal canals in center, often with silica tubercles on epidermis, unbranched or with whorled branches; internodes with longitudinal ridges and grooves. Leaves reduced, scalelike, whorled; lower portion fused to form a collarlike sheath around base of internode; upper portion lobed. Strobili conelike, terminal on stem or branches, terete or ellipsoid, sometimes stalked; sporophylls whorled, peltate, hexagonal in surface view, imbricate, with 5-10 sporangia per sporophyll. Sporangia saclike, in whorls on abaxial side of sporophylls. Spores green, subglobose or globose, 35-70 μm in diam., each with 4 spirally curled, white filaments (elaters) that uncurl upon drying, without colpi, with thin and transparent perispores; perispores with granular ornamentation. Gametophytes growing at or near soil surface, green, disk- to cushion-shaped, irregularly lobed. x = 108.

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 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