Plants terrestrial. Roots blackish, very narrow, tangled, practically glabrous. Stems upright to reclining; hairs few celled, uniseriate. Leaves all fertile or dimorphic with some sterile, lacking blades, mainly unbranched, long-petioled. Fertile blades folded and fistlike or pectinate, pinnate, segments (digits) arising along rachis on distal 3--10 mm; sterile leaves straight or often curling. Sporangia in 2 rows. Gametophytes growing mixed with mosses, green (photosynthetic), delicately filamentous, lacking hairs. x = 77, 94, 103.
Rhizome erect; lvs borne spirally, circinate in vernation, the sterile simple and linear, the fertile with several apical pairs of segments; sporangia sessile, protected by the incurved, long-ciliate lf-margin, erect or slightly bent, the annulus terminal; spores bilateral; gametophyte filamentous. 30, ±cosmop.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
