12a. Pellaea glabella subsp. glabella Mettenius ex Kuhn
Pellaea atropurpurea (Linnaeus) Link var. bushii Mackenzie
Some ultimate segments (especially terminal segments) with hairlike scales abaxially near midrib; most sporangia containing 32 spores; spores averaging 60--72 µm diam. n = 2 n = 116, apogamous.
Sporulating summer--fall. Calcareous cliffs and ledges, usually on limestone substrates; 0--1200 m; Ont., Que.; Ark., Conn., Ill., Ind., Iowa, Kans., Ky., Md., Mass., Mich., Minn., Mo., Nebr., N.Y., Ohio, Okla., Pa., Tenn., Tex., Vt., Va., W.Va., Wis.
G. J. Gastony (1988) has shown that this apogamous tetraploid was derived from Pellaea glabella subsp. missouriensis by an autopolyploid increase in chromosome number.