Entosthodon rubrisetus

Plants 2-5 mm, pale yellow-green. Leaves little contorted when dry, ovate to obovate or spathulate, imbricate, concave, 2-3(-4) mm; margins serrulate distally by projecting ends of thin-walled marginal cells; apices gradually narrowed to a filiform acuminate tip about 425 µm; costa ending 5-8 cells before the acumen; basal laminal cells rectangular (40-55 × 20-25 µm), elongate near margins, distal cells quadrate to oblong polygonal, marginal cells not differentiated. Seta deep brownish red, 6-8 mm, straight, not or scarcely hygroscopic. Capsule deep brownish red, claviform, noticeably gibbous on one side prior to dehiscence, including the long neck that often exceeds half the length, 2-3 mm, mostly retaining shape but the neck sulcate when dry and empty; exothecial cell walls slightly thickened, oblong (3-4:1) and transversely elongate in 3-5 rows proximal to the mouth; operculum pale in contrast to the pigmented capsule and conic-convex, about as high as wide; peristome teeth reddish brown, narrowly lanceolate (85-100 × 10-15 µm), trabeculate basally, becoming hyaline distally and some fusing at the tips, papillose but scarcely striate basally, becoming weakly papillate on the hyaline tips, endostome not seen. Calyptra cucullate, long-beaked, inflated around the capsule, smooth. Spores 24-30 µm, with low papillae.

Sandy soil, canyons and desert washes; moderate to high elevations; Ariz., Calif.

The deep red color of the mature sporophytes serves to help identify Entosthodon rubrisetus in the field or in the herbarium.