Selaginella viridissima
Selaginella viridissima Weath.
(Latin: virdis, green, and -issimus, superlative, very)
Local names: green spike-moss, slenderspike-moss
Plant forming clumps or mounds (to 1 m in diam.), the aerial stems usually erect, radiallysymmetrical, with rhizophores limited to lower . of stems; underground (rhizomatous) stems present, with rhizophores; rhizomes and aerial stems often with a bud-like arrested branch near base; leaves of aerial stems of 1 kind, loosely appressed, linear-lanceolate to narrowly lanceolate, 1.8–2.1 mm long, marginally with only sparse very fine teeth (minutely denticulate), basally cuneate and decurrent to slightly rounded and adnate, apically acute to obtuse, without terminal bristle; strobili solitary, quadrangular, 5–12(–25) mm long; sporophylls apically acute to obtuse. On rock (often igneous), shaded or sheltered ledges, cliffs, crevices, and rocky slopes; in TX known only from the Chisos Mts. of Brewster Co. (Correll 13627, TEX-LL; Warnock 21263, SRSC; Valdespino 1993) and the “Fern Canyon” (Warnock 21694, TEX-LL, US; Carr 2002a) in the Davis Mts. of Jeff Davis Co. (Yarborough & Powell 2002); in the U.S. known only from TX, also Coahuila in n Mexico. Sporulating Jun–Aug. [Bryodesma viridissimum (Weath.) Sojak, S. coryi Weath.] This Chihuahuan Desert endemic (Carr 2002a) is apparently quite rare—it is known from only two counties in the U.S. and a few collections from the n Mexican state of Coahuila (based on Mickel & Smith 2004). The combination of erect habit and leaves without a bristle at the tip is distinctive. Valdespino (1993) noted that the species is of conservation concern and it was one of only two pteridophytes included in Rare Plants of Texas (Poole et al. 2007a); it certainly warrants such designation. (Carr 2002a; Poole et al. 2004, 2007a, 2007b: G2S1)