1. Trichodon cylindricus (Hedwig) Schimper, Coroll. Bryol. Eur. 36. 1856.
Trichostomum cylindricum Hedwig, Sp. Musc. Frond., 107. 1801; Ditrichum cylindricum (Hedwig) Grout
Stems axillary hairs 2 per leaf axil, with 2 short, brown basal cells and 3 elongate, hyaline distal cells. Leaves 1-3 mm, acute, bases ovate; margins plane, serrate to serrulate in subulate part; costa percurrent, filling distal parts of the subula, strongly prorulose distally on abaxial surface; median cells rectangular, 17-39 × 3-5 µm, becoming larger at base. Specialized asexual reproduction sometimes present as yellowish brown, smooth, round or irregularly shaped tubers borne on rhizoids, 65-100 µm in longest dimension; perigonia and perichaetia terminal. Seta orange to red, erect, straight, 0.3-2.7 cm, twisted when dry. Capsule slightly arcuate or sometimes straight (0.5-)1-2(-2.5) × 0.2-0.5 mm; operculum 0.3-0.6 mm.
Varieties 2 (2 in the flora): North America, Eurasia.
Trichodon cylindricus has a disjunct distribution in North America, where it is not uncommon in the northwestern part of the continent but is known from only a few scattered localities in the eastern part. It has been collected from only a single locality each in Michigan (Keewenaw County), New Brunswick, and Ontario, and two localities each in Newfoundland and Quebec. The distinctive gametophytes and sporophytes should aid collectors in finding additional eastern localities. The distinctive characters of this species include the small plants, 2-4 mm high, with squarrose, subulate, acute leaves, and the slender, cylindric capsules.