stem anatomy distinctive, an ectophloic siphonostele, with a ring of discrete xylem strands, these often conduplicate or twice conduplicate in cross-section; stipules at bases of petioles; leaves dimorphicor with fertile portions dissimilar to sterile; sporangia large, with 128–512 spores, opening by an apical slit,annulus lateral; spores green, subglobose, trilete; gametophytes large, green, cordate, surficial; x = 22
