1. Woodsia obtusa (Spreng.) Torr. ssp. obtusa (blunt-lobed woodsia, blunt-lobed cliff fern) Pl. 8e,f; Map 30

Rhizomes prostrate, short-creeping. Rhizome scales concolorous or more commonly bicolorous, brown or dark brown with pale brown margins, lanceolate. Leaves monomorphic, 7–60 cm long. Petioles straw-colored or tan, shorter than the leaf blade, with light brown scales, the bases with 2 vascular bundles. Rachises with small, stalked glands, sometimes also hairy. Leaf blades lanceolate to ovate-elliptic in outline, 1–2 times pinnately compound. Pinnae 0.8–8.0 cm long, narrowly triangular to linear, the tips usually rounded, less commonly acutely pointed, with small, stalked glands, usually also hairy. Pinnules often deeply pinnately lobed, the margins toothed. Veins not anastomosing. Sori circular or nearly so. Indusia attached underneath the sori, cuplike and splitting into several short, irregularly lobed segments at maturity. Spores 64 per sporangium, monolete, 42–47 mm long, brown. 2n=152. May–October.

Scattered throughout the state, relatively common everywhere except in the extreme northwestern corner (eastern U.S. west to Kansas and Texas). Rocky, wooded slopes and shaded ledges of bluffs and outcrops on a variety of substrate types.

Missouri plants of Woodsia obtusa are ssp. obtusa, the widespread tetraploid cytotype, which occurs throughout the range of the species. Windham (1993a) reported the presence of ssp. occidentalis Windham in extreme southwestern Missouri, but did not cite any voucher specimens to support his claim. This diploid progenitor of ssp. obtusa occurs on mostly granite and sandstone ledges on bluffs and rocky slopes from Arkansas and Kansas southwest to central Texas. It is most reliably differentiated from ssp. obtusa by its smaller spores (35–42 mm long) but also tends to have longer-creeping rhizomes, more finely dissected leaf blades, and has the basal pinnules of the lowermost pinnae deeply lobed, rather than toothed to shallowly lobed. This subspecies should be searched for in southwestern Missouri.