Selaginella leucobryoides Maxon
Family: Selaginellaceae
Mojave spikemoss,  more...
Selaginella leucobryoides image
Plants on rock, forming rounded cushionlike mats. Stems decumbent to short-creeping, dry stems readily fragmenting; irregularly forked, without budlike arrested branches, tips straight; main stem upperside and underside structurally slightly different, inconspicuously indeterminate, lateral branches radially symmetric, determinate, strongly ascending, 1-forked. Rhizophores borne on upperside of stems, throughout stem length, 0.2--0.35 mm diam. Leaves monomorphic, ± in alternate pseudowhorls of 4, tightly appressed, ascending, green, linear-oblong to linear-lanceolate, sometimes falcate on lateral rows (on main stem), 2--4.5 X 0.5--0.65 mm (usually smaller on young ascending branches); abaxial ridges present; base cuneate and decurrent (rounded and adnate on young branches), glabrous; margins short-ciliate, cilia transparent, scattered, spreading at base to ascending and dentiform toward apex, 0.07--0.15 mm; apex slightly attenuate and bristled or obtuse and abruptly bristled; bristle whitish or transparent, puberulent, 0.2--0.6 mm. Strobili solitary, 0.4--1.5 cm; sporophylls deltate-ovate or lanceolate, abaxial ridges moderately defined, base glabrous, margins short-ciliate to denticulate, apex acuminate with very short bristle. In rock crevices or on exposed rock; 800--2800 m; Ariz., Calif., Nev. Selaginella leucobryoides has very tightly intertwined stems that readily fragment, a characteristic shared with S . utahensis and S . asprella . Selaginella leucobryoides is very closely related to, and difficult to separate from, S . utahensis (see discussion).

STEMS: monomorphic or slightly dimorphic, the main stem prostrate, with short ascending branches, readily fragmenting when dry, the branch tips appearing straight when dry, forming small, low, dense cushion-like mats. RHIZOPHORES: produced throughout. LEAVES: monomorphic, 2.0-4.5 mm long, linear to narrowly oblong-lanceolate, green to dark green when hydrated, the base decurrent (similar in color to the stem) and more or less symmetrically narrowed, the tip narrowly pointed, sometimes with a straight or somewhat curved white seta 0.2-0.5 mm long (often breaking off with age), this denticulate, the margins relatively short-ciliate, sometimes grading to denticulate distally. STROBILI: 4-15 mm long, the sporophylls broadly lanceolate to ovate-deltate, narrowed to an acute tip with a short seta, the margins denticulate, sometimes short-ciliate proximally MEGASPORES: smooth to finely rugose-reticulate, orange. NOTES: Rock outcrops, ledges, and cliffs, on limestone: Coconino, Mohave cos. (Fig. 1D); 600-1300 m (2000-4300 ft); nw AZ and adjacent s NV and e CA. REFERENCES: Yatskievych, G. and M. D. Windham. 2009. Vascular Plants of Arizona: Selaginellaceae. CANOTIA 5 (1): 39-48.
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