Plants terrestrial, main stems indeterminate, subterranean (rhizomes) or creeping, giving rise laterally to determinate, simple to little-branched branchlet systems; branchlets with leaves spiralled to almost whorled. Leaves all similar or varying in size and shape in different parts of the plant. Strobili erect, terminal or lateral, sessile or stalked. Sporophylls broadly ovate to broadly triangular; sporangia attached to sporophyll base or axillary; spore surface wrinkled. Gametophyte on surface of substrate, tuberous, green, only partly saprophytic.
About 40 species in moist temperate and tropical regions of the world, particularly the Americas; 2 of the 4 Australian species occur in Victoria.