Selaginella corallina
Selaginella corallina (Riddell) Wilbur & Whitson
(Latin: corallum or corallinum from Greek: korallion, red coral, the rationale for the derivation is unclear—the plant has no obvious coral-red color; it is possibly due to the erect habit which resembles in some respects a branched coral)
Local names: Riddell’s spike-moss, Riddell’s selaginella, sand spike-moss
Plants forming clumps, the aerial stems erect to ascending, to ca. 12 cm tall, usually smaller, radially symmetrical, without rhizophores; underground (rhizomatous) stems present, with rhizophores; rhizomes and aerial stems often with a bud-like arrested branch near base; leaves of aerial stems essentially of 1 kind, narrowly triangular-lanceolate to linear-lanceolate, ca. 1.2–3 mm long, 0.4–0.5 mm wide, marginally short ciliate towards base but merely minutely denticulate toward apex, apically with whitish bristle; strobili solitary, sometimes with apical vegetative growth, quadrangular, ascending, (0.5–)1–3(–3.5) cm long and ca.1.2 mm in diam., essentially the same diam. as stems; sporophylls often with a bristle. On rocks (often granite) or terrestrial on sandy or gravelly soils, longleaf pine sand ridges; widespread in e 1⁄2 of TX n to Wood (K. Norton et al. 1031, BRIT), Palo Pinto (R.J. O’Kennon 22178, BRIT), and Cooke (Turner et al. 2003) cos. and w to e Edwards Plateau; AL, AR, GA, LA, OK, and TX. Sporulating throughout the year. [Lycopodium corallinum Riddell, S. riddellii Van Eselt., S. arenicola var. riddellii (Van Eselt.) R.M. Tryon, S. arenicola subsp. Riddellii (Van Eselt.) R.M. Tryon] In the past, TX plants of this species were typically treated as S. riddellii (Correll 1956) or S. arenicola subsp. riddellii (e.g., Diggs et al. 2006). However, there has long been disagreement over the classification and correct name of this and related species (the “arenicola complex”). Tryon (1955) recognized three subspecies, although other authors (e.g., Clausen 1946; Snyder & Bruce 1986) treated the three taxa as separate species. Valdespino (1993) considered the complex to have two species, but maintained subsp. riddellii as a subspecies of S. arenicola. Nauman et al. (2000), did not recognize infraspecific taxa within a broadly defined S. arenicola. Recent research by Wilbur & Whitson (2005) has shown that there is an older name (S. coralline based on Lycopodium corallinum) that has nomenclatural priority and thus must be used according to the International Code of Botanical Nomenclature. The type of S. coralline was collected in TX by Riddell in 1839 (near the San Saba River), and a GH specimen has been identified by Wilbur and Whitson (2005). They also noted that “the rank of species, the first ranking provided for each of the three taxa of the arenicola complex, serves present needs best and is nomenclaturally simplest.” We are therefore following the classification and nomenclature of Wilbur and Whitson (2005) and treating as Selaginella coralline the entity that has been going as S. arenicola subsp. riddellii.