Selaginella underwoodii

Selaginella underwoodii Hieron.
(for L.M. Underwood, 1853–1907 American fern specialist, first fern curator at the New York Botanical Garden, and professor at Columbia Univ.)

Local names: Underwood’s spike-moss

Plants matforming, the mats usually rather loose; stems prostrate-creeping or occasionally pendant, without budlike arrested branches near base, with leaves without strongly upswept or upwardly curved appearance, the leafcovered stems therefore appearing radially symmetrical; rhizophores scattered along entire length of stem; leaves loosely appressed, apically with bristles 0.25–1 mm long, all of one kind, linear to narrowly triangularlanceolate, marginally entire to denticulate to minutely short ciliate, basally mostly cuneate and decurrent; strobili solitary or sometimes paired, quadrangular, 5–35 mm long; sporophylls lanceolate to ovate-lanceolate, apically with short or long bristle. On rock, shaded ledges, cliffs, rocky slopes, on a variety of substrates (e.g., granite, limestone, sandstone); known in TX from Brewster (Chisos Mts., Correll 13668, BRIT, TEX-LL), El Paso (Franklin Mts., E. Whitehouse s.n. 1931, TEX-LL), Jeff Davis (Davis Mts., Correll 34972-A, Warnock 7588, BRIT, TEX-LL), and Val Verde (Z. Labus 56, TEX-LL, Seminole Canyon State Historical Park [e of the Pecos River]; Yarborough & Powell 2002, mapped w of the Pecos River) cos. in the Trans-Pecos and extreme w edge of the Edwards Plateau; AZ, CO, NM, OK, TX, UT, and WY; also n Mexico. Sporulating Jul–Oct. [Bryodesma underwoodii (Hieron.) Sojak, S. fendleri (Underw.) Hieron.] This species can sometimes be found growing in mixed mats with S. mutica and S. peruviana (Yarborough & Powell 2002). It somewhat resembles S. ×neomexicana, “but is distinguished by the leaves being more lax and in fewer ranks than in S. ×neomexicana” (Yarborough & Powell 2002). The prostrate-creeping habit of S. underwoodii also differentiates it from the erect to ascending S. ×neomexicana. Mickel and Smith (2004) described S. underwoodii in Mexico as “a rather distinct species; however, it shows some variation in the number and length of the marginal cilia (from none to many), leaf base pubescence, and arista length.” Because of its rareness and limited distribution in the state, we consider this species to be of conservation concern in TX.

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