Dryopteris Adanson. Woodfern, Shieldfern.
A genus of about 400 species, nearly cosmopolitan, but concentrated in temperate Asia. Sessa, Zimmer, & Givnish (2012) discuss the phylogeny and biogeography of Dryopteris; the clades shown in the key are from their work.
ID notes: Dryopteris and Athyrium are often confused when not fertile; they can be easily distinguished by breaking off a leaf and counting vascular bundles (which will appear as thread-like strands). Dryopteris has 5 and Athyrium has 2. Many Dryopteris species will hybridize with one another to form sterile hybrids. Whenever two or more Dryopteris species are found growing together, there is a good chance that hybrids are present. Hybrids generally show intermediacy between the two parents, and have abortive sporangia or spores.
Ref: Hoshizaki & Wilson (1999); Kees & Weakley (2018) In Weakley et al. (2018b); Kramer & Green (1990); Montgomery (1982); Montgomery & Paulton (1981); Montgomery & Wagner (1993) In Flora of North America Editorial Committee (1993b); Sessa, Zimmer, & Givnish (2012); Umstead & Diggs (2018); Wyatt (2020). Show full citations.