Athyrium Roth, Tent. Fl. Germ.

Kessler, Michael & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. XXXII. Athyriaceae, Phytotaxa 334 (2), pp. 141-151 : 142

Athyrium Roth, Tent. Fl. Germ. 3(1): 31, 58–59. 1800.

Athyrium is a genus of worldwide distribution with about 230 species, most of which occur in eastern and southeastern Asia ( Adjie et al. 2008). It often has J-shaped, elongate sori with the indusium hooking over the vein tip. Circumscription of the genus, with regard to inclusion or not of several paleotropical genera, e.g., Cornopteris , Pseudocystopteris , and Anisocampium , is still not entirely settled ( Sano et al. 2000, Rothfels et al. 2012b), but the tendency is to subsume a number of segregate genera under a broadly defined Athyrium . It is most closely related to Diplazium ( Wang et al. 2002, Rothfels et al. 2012a, 2012b) from which it differs by sorus position and shape, thinner blade texture, occurrence at generally higher elevations, and chromosome base number (40 in Athyrium , 41 in Diplazium ). Based on general habit, Athyrium can be confused with some species of Polystichum ( Dryopteridaceae ), which usually have more numerous reddish to brownish or blackish, persistent petiole scales, and spinulose segment margins ( Kessler et al. 2017). Megalastrum ( Dryopteridaceae ) differs is having long, hairlike, marginally toothed scales on petiole bases and blade midribs, veins ending before the segment margins (as seen adaxially), and stout, curved, often septate hairs on the costae and costules adaxially (and sometimes abaxially). The neotropical species of Athyrium are in need monographic study.