5. Selaginella wrightii Hieronymus, Hedwigia. 39: 298. 1900.
Plants on rock, forming loose to dense mats. Stems not readily fragmenting, prostrate, upperside and underside structurally different, irregularly forked, branches determinate, tips upturned. Rhizophores borne on upperside of stems, throughout stem length, 0.25--0.37 mm diam. Leaves dimorphic, arranged in 8 ranks, tightly appressed, ascending, green; abaxial ridges absent; apex with yellowish bristle 0.2--0.5 mm, becoming denticulate (by breaking off of bristle); bristle usually more persistent in underside leaves. Underside leaves narrowly linear-lanceolate to falcate (on marginal ranks), 3.5--4.5(--5) X 0.55--0.7 mm; base abruptly adnate or slightly decurrent, usually pubescent, sometimes glabrous; margins ciliate, cilia transparent, spreading, 0.12--0.26 mm. Upperside leaves linear-lanceolate, 3.3--3.85 X 0.6--0.75 mm; base abruptly adnate, pubescent; margins ciliate, cilia transparent, spreading, 0.12--0.26 mm. Strobili solitary, (0.7--)1.5--2(--2.6) cm; sporophylls lanceolate, abaxial ridges not prominent, base glabrous, margins ciliate, apex strongly tapering, bristle obscure.
On exposed or shaded limestone cliffs; of conservation concern; 800--2300 m; N.Mex., Tex.; Mexico.
Of other species in the flora, Selaginella wrightii seems to be allied to S . hansenii . The structural differentiation of the stem, adjacently different leaves, and upturned branch tips align the two species to the series Eremophilae . Selaginella wrightii is a calciphile, according to R. M. Tryon (1955).