Rosulabryum bornholmense
Novon 19: 398. 2009.
Plants small, red-green. Stems 0.5–2 cm, fertile stems evenly foliate to weakly rosulate, innovations evenly foliate. Leaves of main rosette and innovations similar, innovation leaves smaller; somewhat irregularly twisted to contorted when dry, erect-spreading when moist, ovate, weakly concave, 1–2 mm; base not decurrent; margins recurved to mid leaf, weakly but distinctly serrulate distally, limbidium moderately distinct, of 1 or 2 rows of cells; apex acute; costa excurrent, awn pigmented; proximal laminal cells short-rectangular; medial and distal cells rhomboidal, 14–20 µm wide, 3–4:1, walls thick, not porose. Specialized asexual reproduction by rhizoidal tubers, amber, orange, orange-red, or dark red, becoming orange-brown, pale brown, or dark brown when old, usually brighter than rhizoids, (120–)180–350 µm, cells not or only weakly protuberant. Sexual condition dioicous, synoicous, or autoicous. Capsule nutant, red to red-brown, cylindric, 2–3 mm.
Phenology: Capsules mature Apr–Aug.
Habitat: Disturbed soil
Elevation: low elevations (100 m)
Distribution
Calif., Europe.
Discussion
A. C. Crundwell and H. L. K. Whitehouse (2001) revised Rosulabryum bornholmense, providing new criteria to separate it from the closely related R. rubens. In addition to tuber and awn differences, the cells of the tubers in R. bornholmense are 45–60 µm wide, while those of R. rubens are 30–35 µm wide. Most North American collections can be referred to the latter species.