Trichostomum cylindricum Hedwig
Stems 2--4 mm, simple; 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 portion of subula, strongly prorulose distally on abaxial surface; median cells rectangular, 17--39 ´ 3--5 µm, becoming larger at base. Specialized asexual reproduction by yellowish brown, smooth, round or irregularly shaped tubers, 65--100 µm, sometimes present on rhizoids. Perigonia and perichaetia terminal. Seta orange to red, erect, straight, 0.3--2.7 cm, twisted when dry. Capsule yellowish to reddish brown, slightly arcuate or sometimes straight (0.5--)1--2(--2.5) ´ 0.2--0.5 mm; operculum 0.3--0.6 mm. Spores 9--24 µm.
Varieties 2 (2 in the flora): North America, Europe, Asia.
Trichodon cylindricus has a disjunct distribution in North America, where it is not uncommon in the Northwestern but is known from only a few scattered localities in the East. It has been collected only from a single locality in Michigan (Keewenaw Co.), New Brunswick, Ontario and two localities in Newfoundland and Quebec. Although it is rare in the East, the distinctive gametophytes and sporophytes should aid collectors in finding additional localities. The distinctive characters of this species include its short stems (2--4 mm), with squarrose, subulate, acute leaves, and slender, cylindric capsules.
