Pellaea glabella
Pellaea glabella Mett.
ex Kuhn. subsp. glabella, (Latin: glaber, without hair, plus the diminutive suffix, -ella, signifying tiny or small)
Local names: smooth cliff-brake
Plant to 40 cm tall; rhizome scales uniformly colored, reddish brown; petioles dark brown, shiny; leaf blades 1-pinnate or usually 2-pinnate below, 1–8 cm wide, monomorphic; rachis and costae glabrous; pinnae attached to rachis so that their tips point more or less straight out or slightly towards tip of leaf, the basal pinnae sessile to short-stalked (stalks less than 5 mm long), the upper pinnae sessile; ultimate leaf segments oblong-lanceolate, apically obtuse, leathery to herbaceous, glabrous except some ultimate segments with hair-like scales on lower surface near midrib; n = 2n = 116 (Windham 1993c). Cliffs and ledges, in crevices, on limestone or calcareous sandstone; in TX known only from Potter Co. (Correll & Correll 13085, along John Rey Creek, in crevices of dry limestone, 1946, BRIT, TEX-LL; Turner et al. 2003, in the High Plains); widespread in the ne U.S. (and adjacent s Canada) s to NC, TN, and AR, and w to MI, KS, and OK, disjunct to the TX Panhandle. Sporulating Jun–Oct. [P. atropurpurea var. bushii Mack. & Bush] Pellaea glabella is currently recognized as being made up of 4 geographically isolated subspecies (Windham 1993c); subspecies glabella is an apogamous tetraploid (Windham 1993c). Prior to the use of molecular techniques, it was thought that this tetraploid might have arisen as a hybrid involving P. atropurpurea; however, research by Gastony (1988) and Gastony et al. (1992) conclusively showed this was not the case. It appears to be an autotetraploid derived from the diploid P. glabella subsp. missouriensis (Gastony) Windham, known only from Missouri. Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.