Bryum radiculosum Bridel, Muscol. Recent., suppl. 3: 18. 1817

Plants small, green or yellow-green, often with reddish tinge. Stems 0.5-1(-2) cm; rhizoids yellow-red, brown, or red-brown. Leaves loosely set, broadly lanceolate to narrowly ovate, weakly concave, 0.4-1.5(-2) mm; base not decurrent; margins plane to revolute proximally, serrulate distally, limbidium absent; apex acute to acuminate; costa short- to long-excurrent, awn slender, ; alar cells similar to adjacent juxtacostal cells; proximal laminal cells abruptly quadrate to occasionally short-rectangular, 1-2:1; medial and distal cells 40-60 × 10-12(-14) µm, 3-5:1. Specialized asexual reproduction by rhizoidal tubers, on long rhizoids in soil, red to red-brown, spheric, 120-180 µm, cells 20-40 µm, smooth. Sexual condition dioicous. Capsule inclined or nutant, 2-3 mm.

Capsules mature Apr-Jul (spring-summer). Dry disturbed calcareous soil, soil over rock; low to moderate elevations (0-1500 m); Calif., Nev., Oreg.; Mexico; West Indies; Europe; e Asia (Japan); n Africa; Atlantic Islands (Canary Islands); Australia.

Gemmabryum radiculosum is distinguished by the relatively large, reddish, spheric tubers with smooth cells, similar in color to the rhizoids, long-excurrent costa, and preference for strongly calcareous substrates. Gemmabryum subapiculatum is similar, but with red tubers that are brighter than the rhizoids, a short-excurrent costa, and a preference for acidic substrates.