Plants 1-10 cm, in tall tufts, blackish proximally, yellowish brown distally. Leaves 4-10 mm, straight in wet and dry state, narrowly lanceolate, those of deciduous stem tips often even longer and narrower, ending in a very long subula; alar cells auriculate, hyaline or red-brown; basal laminal cells usually shortly rectangular to subquadrate, thick-walled with pitted walls, 4-8 rows of elongate hyaline cells at basal margins of leaves; distal laminal cells elongate oval to vermicular, walls incrassate; costa filling 1/2-2/3 of leaf width, excurrent in a long, straight, spinose-dentate hyaline hairpoint, in transverse section showing adaxial hyalocysts as wide as the median deuters, and abaxial groups of stereids, weakly ribbed at back. Specialized asexual reproduction by broken stem tips. Seta 4 mm. Capsule 1.5 mm, ovoid, brownish, operculum obliquely rostrate.
Varieties 2 (2 in the flora): North America, Europe, Asia.
Campylopus atrovirens is similar to C. sinensis, which differs by shorter, not vermicular distal laminal cells and shorter hyaline leaf tips. The latter has been found only once, in British Columbia, but it could be that collections of C. sinensis from the west coast of North America have been misidentified as C. atrovirens.
Leaves gradually contracted into a long, fine point, hyaline at the extreme apex.
Wet rocks, damp cliffs, seepage banks, bogs or wet humic soil, always in open habitats at sea level along the coast, or at about 1500 m in the Appalachian Mountains; 0-1500 m; B.C., Nfld. and Labr. (Nfld.); Alaska, N.C., Wash.; Europe; Asia.
The population in the Appalachian Mountains differs by greenish, not blackish plants, smaller size, less developed alar cells and less incrassate, basal laminal cell walls. Such plants have been described from similar habitats and similar elevations from the Alps of Europe as Campylopus adustus De Notaris. It is not known whether these populations in non-coastal areas are genotypically different or just modifications associated with higher elevations. It may perhaps deserve to be recognized at the varietal rank. Forms with falcate leaves as occurring in Europe or Asia have not yet been found in North America. Sporophytes, produced very rarely, were found in North America only once, in British Columbia