2a. var. glabella
Spores 60–72 mm
in diameter, 32 per sporangium. 2n=116 (apomictic). April–October.
Scattered throughout the Ozark and Ozark Border Divisions, locally north to
Andrew, Knox, and Lewis Counties (northeastern U.S.
and adjacent Canada,
southwest to Kansas and Texas). Crevices and ledges of limestone and
dolomite bluffs, boulders, and rock outcrops, rarely on sandstone.
This is the common, 32-spored, apomictic variety of the species. Where it
occurs with var. missouriensis, hybrids between the two varieties can be
found. These are fertile, pentaploid (2n=145) apomicts. They are
morphologically indistinguishable from var. glabella, even by spore
size, and were first identified using genetic markers (allozymes) (Gastony,