Selaginella scopulorum
Selaginella scopulorum Maxon
(Latin: scopula, rock, cliff, or crag, the type specimen described as growing on “rocks”)
Local names: rocky mountain spike-moss
Plant forming flat cushion-like mats (in TX, in other parts of the range the mats can be loose); stems prostrate-creeping, with upper and lower surfaces slightly different in appearance, without budlike arrested branches near base; rhizophores scattered along entire length of stem; leaves tightly appressed, linear-lanceolate to linear and sometimes falcate, marginally short ciliate at base but merely minutely denticulate toward apex, the apices bristled, the bristles 0.5–1.1 mm long, whitish, the leaves all of one kind though those on underside of stems glabrous and decurrent at base, marginally short ciliate, those on upper side of stem slightly smaller, glabrous or rarely pubescent and slightly decurrent to adnate at base; strobili solitary, quadrangular, (5–)10–30(–45) mm long; sporophylls lanceolate to ovate-lanceolate, rarely ovate, apically with short bristle. On rock or terrestrial, typically in rather dry habitats (outcrops, rocky slopes, ledges, talus slopes), often on igneous or sandstone substrates; in TX known only from sandstone outcrops 3 mi e of Study Butte in s Brewster Co. (J.A. Moore & J.A. Steyermark 3245, US [xerox of specimen at SRSU], identified as S. densa var. scopulorum by R. Tryon & T. Reeves; Tryon 1955; Correll 1956 [in Addenda];Yarborough & Powell 2002); n British Columbia s to CA (along the Cascades) and s to TX along the Rocky Mts. Sporulating ?–Jun–Jul–? [S. densa var. scopulorum (Maxon) R.M. Tryon, S. engelmannii var. scopulorum (Maxon) C.F. Reed] This species has a very broad range along the Rocky Mts. and occurs in a variety of habitats—alpine tundra to mountains in the Chihuahuan Desert of sw TX—its TX occurrence is the most southerly record known. It could be referred to as a “Rocky Mt. disjunct” since its TX location is disjunct by approximately 300 mi/480 km from its nearest other known occurrence in New Mexico. It is part of the S. densa Rydb. complex, which is in need of taxonomic work (Valdespino 1993). Yatskievych and Windham (2009b) treated this taxon as S. densa var. scopulorum. Specimens from the TX population “are yellow-green in color and have very short, tufted branches that form a flat, cushiony mat” (Yarborough & Powell 2002). Given its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.