Plants on rock, forming clumps or mounds. Stems radially symmetric, underground (rhizomatous) and aerial, not readily fragmenting, irregularly forked; rhizomatous and aerial stems often with 1 branch arrested, budlike, tips straight; aerial stems mainly erect, seldom ascending, with budlike arrested branches throughout stem length. Rhizophores borne on upperside of stems, restricted to rhizomatous stems and lower 1/4 of aerial stems, 0.16--0.3 mm diam. Leaves dimorphic, not clearly ranked. Rhizomatous stem leaves loosely appressed, straight, scalelike. Aerial stem leaves appressed, ascending, green, linear-lanceolate to narrowly lanceolate, 1.8--2.1 X 0.49--0.56 mm; abaxial ridges prominent; base cuneate and decurrent to slightly rounded and adnate, glabrous; margins denticulate to very short-ciliate, cilia transparent, spreading to ascending toward apex, 0.02--0.04 mm; apex acute or seldom blunt. Strobili solitary, 0.5--1.2(--2.5) cm; sporophylls deltate-ovate to ovate-lanceolate, abaxial ridges prominent, base glabrous, margins denticulate, apex acute to obtuse.

Shaded cliffs, slopes, rock crevices, and igneous rock; of conservation concern; 1650--2300 m; Tex.; Mexico in Coahuila.

In Texas Selaginella viridissima is known only from the Chisos Mountains.

Common Name: green spikemoss Rarity: G2 Etymology: Selaginella is a diminutive of Selago, the name of another similar plant,