Thelypteris palustris Schott
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Rhizome with a few appressed, ovate scales, otherwise glabrous; lvs subdimorphic; petioles black at the base, glabrous, scaleless, the sterile to 3.5 dm, shorter or longer than the blades, the fertile to 7 dm, longer than the blades; blade lanceolate or lance-oblong, to 4 × 2 dm, pinnate-pinnatifid, acuminate, only slightly narrowed at the base; pinnae lance-linear, subsessile, the sterile to 2 cm wide, with obtuse, entire, broadly oval segments to 10 × 5.5 mm, the fertile segments oblong, to 4 mm wide, with incurved margins; costae scarcely scaly, these and the costules hairy; veins 6–8 pairs per segment, those of the sterile blades once forked, those of the fertile blades simple or the basal ones mostly forked; indusia ciliate or rarely glabrous; 2n=70. Marshes and bog-margins; widespread in the N. Hemisphere, and throughout our range. (Aspidium thelypteris; Dryopteris thelypteris) Our plants are var. pubescens (Lawson) Fernald.