Tree-ferns, with large fronds crowning an erect, thick trunk. Stipe very thick, with a discontinuous line of pale aerating tissue along each side, clothed in scales. Fronds pinnate. Sori borne between margin and midvein, with or without indusium; receptacle large, bearing shortly stalked sporangia; annulus oblique. Gametophyte cordate.
2 genera (but see Tryon 1970) with c. 700 species in tropical, subtropical and more rarely, temperate regions of the world.