Cystopteris bulbifera (L.) Bernh.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Larger and coarser than no. 1 [Cystopteris fragilis (L.) Bernh.] , the lvs 3–8(–15) dm, the blade 6–9 cm wide, with (15–)20–30 pairs of pinnae, the lowest pair a little larger than the next pair, the reduced upper pinnae more numerous than in no. 1, so that the lf tapers more gradually to the tip; rachis commonly with 1 or more well developed bulbils on the lower side beyond the middle, these to 4 or 5 mm; costae with scattered pale short-stalked glands; veins mostly ending in the smaller sinuses (reflecting an exaggeration of the tendency seen in some specimens of no. 1 for the principal teeth to be apically indented); indusium brownish, rounded or truncate at the tip, bearing scattered small, pale, short-stalked glands; 2n=84; otherwise much like no. 1 [Cystopteris fragilis (L.) Bernh.].