Nyholmiella gymnostoma (Bruch ex Bridel) Holmen & E. Warncke

Plants 0.4-1.2 cm. Stem leaves erect-appressed when dry, ovate to ovate-oblong, 2-2.8 mm; margins involute, entire; apex rounded to obtuse; basal laminal cells elongate-rectangular, walls thick, not nodose; distal cells 7-12 µm, 1-stratose, papillae 2 or 3 per cell, conic, small. Specialized asexual reproduction by gemmae on adaxial surface of leaves. Sexual condition dioicous. Seta 0.5 mm. Capsule immersed, oblong, 1.8 mm, moderately 8-ribbed when dry; stomata superficial; peristome and prostome absent. Calyptra conic, papillose, naked, . Spores 18-20 µm.

Bark of deciduous trees; low to moderate elevations (0-200 m); Nfld. and Labr. (Nfld.); Europe; e Asia (Japan).

Orthotrichum gymnostomum differs from the similar O. obtusifolium by its leaves with involute margins, laminal cells with two or three papillae, and immersed capsules with no peristome, while O. obtusifolium has leaves with erect margins, 1-papillose cells, and emergent capsules with a double peristome. Orthotrichum gymnostomum is rare in North America, restricted to the coastal areas of Newfoundland.