Stems compact to short-creeping, individual branches usually 5--10 mm diam. Blade coarsely cut and evidently 2-pinnate. Proximal pinnules of lower pinnae usually shallowly lobed or merely dentate. Spores averaging 42--47 µm. 2 n = 152.

Sporulating summer--fall. Cliffs and rocky slopes (rarely terrestrial); found on a variety of substrates including both granite and limestone; 0--1000 m; Ont., Que.; Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.

D. F. M. Brown (1964) hypothesized that tetraploid Woodsia obtusa might be an autopolyploid derived from W . oregana . Recent isozyme and spore ornamentation studies indicate, however, that these species are not closely related, and the discovery of a diploid cytotype of W . obtusa suggests a different (albeit autopolyploid) origin for this taxon (M. D. Windham 1993). Tetraploid subsp. obtusa crosses with diploid subsp. occidentalis ; the resulting triploids are sterile and have malformed spores. It also hybridizes with W . oregana subsp. cathcartiana to form the sterile tetraploid hybrid known as W . × kansana Brooks.

Infrequent to rare in the southern part of the state and very local northward to the counties shown on the map. Probably not found in Indiana north of the counties shown on the map. It no doubt occurs also in Wabash County but I have not been able to find it. It is usually found in shallow soil on rocky slopes. It prefers sandstone but is also found on limestone.