Pellaea glabella subsp. missouriensis
Contr. Univ. Michigan Herb. 19: 39. 1993.
Some ultimate segments (especially terminal segments) with hairlike scales abaxially near midrib; sporangia containing 64 spores; spores averaging 38–52 µm diam. 2n = 58.
Phenology: Sporulating summer–fall.
Habitat: Cliffs and ledges, apparently confined to limestone
Elevation: 100–300 m
This diploid taxon is currently known only from southeastern Missouri in the Ozark region, but a thorough survey of spore number per sporangium in Pellaea glabella from eastern North America may yield additional localities. Plants of P. glabella subsp. missouriensis occasionally hybridize with P. glabella subsp. glabella; the hybrids are apogamous pentaploids resembling P. glabella subsp. glabella (G. J. Gastony 1988).