17. Dicranum spadiceum J. E. Zetterstedt, Kongl. Svenska Vetensk. Acad. Handl. 5(10): 20. 1865.
Dicranum angustum Lindberg; D. laevidens R. S. Williams
Plants in loose to dense tufts, green to yellowish green or brown, glossy. Stems 2.5-7 cm, densely tomentose with reddish brown rhizoids. Leaves straight, erect-spreading, little changed when dry, smooth, (4-)5.5-8(-9) × 0.5-1 mm, concave below, tubulose above, from a lanceolate base to a long-acuminate subula, apices acute or sometimes ± blunt; margins entire or slightly serrate in the distal 1/3; laminae 1-stratose; costa percurrent to shortly excurrent, 1/10-1/6 the width of the leaves at base, smooth to slightly rough above on abaxial surface, abaxial ridges absent, with a row of guide cells, 2 well-developed stereid bands extending almost to apex, abaxial epidermal layer of cells differentiated, rarely some cells in adaxial epidermal layer enlarged; cell walls between lamina cells not or slightly bulging; leaf cells smooth; alar cells 2-stratose, well-differentiated, not extending to costa; proximal laminal cells elongate, pitted, (16-)36-62(-112) × (3-)7-8(-20) µm; distal laminal cells short-rectangular to irregularly angled, pitted, (9-)10-17(-31) × (3)7-8(18) µm. Sexual condition pseudomonoicous; dwarf males on rhizoids of female plants; interior perichaetial leaves abruptly acuminate, convolute-sheathing. Seta 2.5-3.5 cm, solitary, rarely 2 per perichaetium, yellow to reddish yellow. Capsule 2-3.5 mm, arcuate, inclined, furrowed when dry, light to dark brown; operculum 1.5-2.8 mm. Spores 14-22 µm.
Capsules mature in summer. Fens, wet meadows, willow thickets, or humus or soil on or around rocks at lake margins; occasionally drier habitats, such as beach ridges; 10-2300 m; Greenland; Alta., B.C., Man., Nfld. and Labr. (Nfld.), Nunavut, Ont., Que., Sask., Yukon; Alaska, Colo., Mont., Utah, Wyo.; Europe; Asia.
Dicranum spadiceum has been reported from Saskatchewan by G. Bellolio-Trucco and R. R. Ireland (1990), Colorado by W. L. Peterson (1979), Montana by S. Eversman and A. J. Sharp (1980), and Utah by S. Flowers (1973). It is an arctic-alpine species known principally by the 4-9 mm, straight, erect-spreading leaves, scarcely changed when dry, concave below, tubulose above, narrowed from a lanceolate base to a long-acuminate subula ending in an acute to ± blunt apex; the elongate, pitted cells throughout the leaf; and the costa that is smooth to somewhat rough above on the abaxial surface. Dicranum angustum Lindberg, often considered distinct because of its blunt leaf apices, is considered a synonym after examination of its type from Europe (see discussion by Bellolio-Trucco and Ireland).