Bull. Torrey Bot. Club 25: 130. 1898.
Plants on rock or terrestrial, forming clumps. 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 erect or occasionally ascending. Rhizophores borne on upperside of stems, restricted to rhizomes and lower 1/3 of aerial stems, 0.3–0.4 mm diam. Leaves dimorphic, not clearly ranked. Rhizomatous stem-leaves persistent, tightly appressed, scalelike. Aerial stem-leaves appressed, ascending, green, linear-lanceolate to narrowly lanceolate, 2.2–3.8 × 0.29–0.4 (–0.75) mm; abaxial ridges present; base abruptly adnate, cordate to almost peltate, pubescent or sometimes glabrous; margins short-ciliate at base, denticulate toward apex, cilia white to transparent or greenish, spreading at base, ascending toward apex, 0.02–0.08 mm; apex keeled, bristled; bristle puberulent, rough, transparent to whitish, 0.23–0.75 mm. Strobili solitary, (0.4–) 1–1.5 cm; sporophylls ovatelanceolate to lanceolate, abaxial ridges not prominent, base glabrous, margins short-ciliate to denticulate, apex bristled. 2n = 18.
Habitat: Exposed rock crevices, cliffs, boulders, sandstone or igneous rock, serpentine, or gravelly soil
Elevation: 0–2000 m
Calif., Mexico in Baja California
Selaginella bigelovii is a member of the series Arenicolae (R. M. Tryon 1955) and is closely related to S. rupincola (see discussion). It may be confused with S. × neomexicana. Selaginella bigelovii, however, always has well-developed megasporangia with most of the megaspores and microspores well formed, whereas S. × neomexicana is a presumed sterile hybrid that does not form megaspores, seldom forms microspores, and usually has most sporangia misshapen (R. M. Tryon 1955). Moreover, S. × neomexicana has not been reported from either California or Baja California.
"thick" is not a number.