Polypodium virginianum L.
Polypodium vulgare auct. non L. p.p.
Polypodium vulgare L. var. virginianum (L.) Eaton
Common Polypody, Rock Polypody, Rock Cap Fern
Rock polypody is native to eastern North America, and possibly also to Japan, Korea, Mongolia, and eastern Siberia. It forms a springy, verdant carpet over rocks, even in winter. It is also partial to cliffs. It prefers dampness and shade.
Identification: Smaller than most ferns, rock polypody has narrow fronds 3-16" (8-40 cm) long and 1-2" (3-6 cm) wide, on smooth stems (petioles) 1-6" (3-15 cm) long. Fronds are erect and often arched, oblong, lanceolate-oblong, or elliptic-oblong in general shape, containing 8-20 pairs of leaflets, and usually widest toward the middle. While many ferns emerge from a central rhizome, these are haphazardly oriented. Leaflets are oblong and acuminate. The angle formed between successive leaflets is very acute, while similar appearing resurrection ferns’ are concave. In summer and fall, round sori, arranged in neat rows and columns of fuzzy-looking pale brown dots, appear on the leaf undersides. The sori lack a protective membrane (indusia).
Polypodium virginianum at Illinois Wildflowers
Polypodium virginianum on the New England Wildflower Society’s GoBotany site
Polypodium virginianum on Wikipedia
Cobb, Boughton, Farnsworth, Elizabeth & Lowe, Cheryl, Peterson Field Guides: A Field Guide to Ferns and Their Related Families of Northwestern and Central North America, Houghton Mifflin Company, 2005, p. 194
Polypodium virginianum description by Thomas H. Kent, last updated 25 Oct 2018.