Rhytidiadelphus squarrosus subsp. japonicus Reimers, Bot. Jahrb. Syst. 64: 559. 1931

Plants to 7 cm, soft. Stems 3-5 mm wide across leafy stem, remotely and irregularly branched to irregularly 1 (or 2)-pinnate, branches to 1.5 cm. Stem leaves wide-spreading to squarrose, not crowded, broadly ovate, not plicate or rugose, 2.1-3.8 × 1.6-3.2 mm; base scarcely sheathing, broadly rounded to insertion; apex abruptly narrowed, acumen short, channeled; costa 1/3-1/2 leaf length; alar cells vaguely distinct, slightly wider than basal cells, walls thick, porose; medial laminal cells 25-55 × 4-7µm, smooth. Branch leaves ovate, 1.5-2.8 × 0.7-2 mm. [Capsule oblong, 2.1 mm].

Under tall forbs in coastal meadows of lower mountain slopes; low elevations (0-30 m); Alaska; e Asia.

Rhytidiadelphus japonicus is known from five or fewer localities in North America, all in the Aleutian Islands.