Musc. Buitenzorg 4: 1245. 1923.
Plants small, reclining, pale yellow-green. Stems 0.5–5 cm, to 1 mm wide across main leafy shoot, somewhat complanate-foliate, little or irregularly branched, branches sometimes flagelliform; pseudoparaphyllia narrowly lanceolate. Leaves slightly secund to falcate, occasionally almost erect, ovate-lanceolate, tapering to apex, 0.8–1.2 cm; margins toothed in acumen; alar cells 2 or 3, red-brown. Sexual condition autoicous. Seta red-brown, 0.5–1 cm. Capsule suberect, cylindric, symmetric to somewhat asymmetric; operculum rostrate.
Phenology: Capsules mature winter.
Habitat: Tree trunks and bases, organic soil, forest margins
Elevation: low to high elevations
In the genus, plants of Brotherella roellii are those of smallest stature in North America. It is the only autoicous species, thus sporophytes are fairly common. When sterile, however, B. roellii commonly produces readily deciduous flagelliferous shoots or branches. The species appears to be extinct in Washington; no specimens have been collected there for more than 70 years. In British Columbia, most collections have been made in secondary forests or on forest edges.