Selaginella arizonica

Selaginella arizonica Maxon
(of Arizona, where the type specimen was collected)

Local names: Arizona spike-moss

Plant forming loose mats; stems prostrate, with upper and lower surfaces different in appearance (leaves upswept or curving upward making the views of the leaf-covered stems from above and below distinctly different); rhizophores scattered along entire length of stem; leaves tightly appressed to ascending, apically merely acute or with very short flattened bristle 0.3 mm or less long (bristles mostly only on leaves at branch tips or buds), all of one kind though leaves on underside of stems widest at middle (lanceolate in outline), glabrous and decurrent at base, marginally ciliate, those on upper side slightly shorter and narrower, abruptly adnate at base, marginally ciliate; strobili solitary, quadrangular, 5–10 mm long, sporophylls ovate-deltate, apically merely acute to acuminate, lacking bristle. On rock or terrestrial, slopes, gravel, crevices, and ledges, on various substrates (e.g., sandstone, igneous, rarely limestone); mainly Brewster (e.g., Correll 13594, 29752, TEX-LL) and Presidio (e.g., Correll 13741, TEX-LL) cos. in sc Trans-Pecos, also Sierra Diablo Mts. in Culberson Co. (Yarborough & Powell 2002) and s Jeff Davis Co. (Turner et al. 2003); AZ, TX; also n Mexico. Sporulating Jul– Oct. [Bryodesma arizonica (Maxon) Sojak] This species is similar to S. peruviana, but is “most easily distinguished by the thin, lanceolate leaves on the underside of the stem and the lack of bristles on the sporophylls” (Yarborough & Powell 2002). In comparison, S. peruviana has fleshier, narrower (linear to linear-lanceolate) leaves and sporophylls with bristles. Arizona spike-moss can sometimes be found growing “intertwined with S. rupincola” (Yarborough & Powell 2002). Yatskievych and Windham (2009b) noted that, “Where S. arizonica co-occurs with the morphologically distinctive S. rupincola, occasional putative hybrids also are encountered with intermediate morphology and abortive spores.” Given its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.

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