Terrestrial or epiphytic perennial herbs. Rhizome short. Roots thick and fleshy. Fronds simple or divided, not coiled in bud, composed of stipe, sterile lamina and fertile spike. Sporangia aggregated into spike, fused together or free, spherical. Spores of one sort only, numerous, thick-walled. Gametophyte subterranean, tuberous, bearing copious rhizoids, associated with fungus.
3 genera with c. 90 species; 2 genera represented in Victoria (Helminthostachys, with palmate sterile fronds, occurs in tropical Australia).