Gymnocarpium robertianum (Hoffm.) Newman
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Much like no. 1 [Gymnocarpium dryopteris (L.) Newman] ; blade green, densely and finely glandular (as also the petiole), a little narrower, deltoid, to 14 × 16 cm; segments of the basal pinnae ovate-oblong, obtuse, sessile, the lowest basal one mostly less than a fourth as long as the main rachis; ultimate segments to 9 mm, with entire to crenate, mostly recurved margins; 2n=160 (ours). On calcareous rocks; circumboreal, s. to Pa., Mich., Io., and Ida. (G. jessoense; Dryopteris r.; Phegopteris r.)