Montane Dicranum Moss

Dicranum montanum is one of the smallest species of the genus in North America. It can best be recognized by the small plants, often only 1-2 cm, the dull, yellowish green to dark green leaves that are strongly crisped when dry, the lanceolate, acuminate leaves that are subtubulose to keeled above, rough on the abaxial surface near the apex, and the straight, erect capsules. Also aiding in its recognition is the occasional presence of small, delicate, clustered branchlets with linear leaves that are readily detachable (probably a means of asexual reproduction), which occur near the stem apices. The detached leaves from the branchlets leave characteristic scars on the denuded portions. Dicranum montanum can sometimes be mistaken for D. flagellare, its closest relative, especially when the latter species does not have its typical flagelliform branchlets in the leaf axils or when they have been overlooked. Dicranum montanum has leaves with a keeled subula in the distal half, with a strongly papillose or toothed abaxial surface near the apex and distal leaf cells that are regularly quadrate. Dicranum flagellare, in contrast, has leaves with a tubulose subula above, with the abaxial surface usually smooth, and mostly short-rectangular leaf cells.

Plants in dense tufts, usually with weak, clustered branchlets near stem apices with small, linear, erect-spreading, costate leaves, strongly crisped when dry, yellowish green to dark green, dull. Stems 0.5-3(-5) cm, densely tomentose with white to reddish brown rhizoids. Leaves erect-spreading, cirrate to strongly crisped when dry, smooth, (1-)2-3(-4) × 0.2-0.5 mm, concave below, subtubulose to keeled above, lanceolate at base, acuminate above to an acute apex, rough above on abaxial surface; margins irregularly serrate to serrulate in distal half of leaves; laminae 1-stratose; costa percurrent to shortly excurrent, ¹/6-¹/4 the width of the leaves at base, rough with papillae or teeth on abaxial surface in distal half of leaf, abaxial ridges absent, with a row of guide cells, two weakly developed stereid bands above and below, not extending to the leaf middle, adaxial and abaxial epidermal layers of cells not differentiated or with a few cells enlarged in both layers; cell walls between lamina cells not bulging; leaf cells smooth below, mammillose or usually abaxially prorate or toothed in distal half of leaves, giving leaves a dull appearance; alar cells 1-stratose, differentiated or sometimes indistinctly differentiated, not extending to costa; proximal laminal cells rectangular to oblong-rectangular, not pitted or with few pits, (10-)20-32(-50) × (4-)6-8(-13) µm; distal laminal cells usually quadrate to short-rectangular, some cells transversely elongate, not pitted, (5-)8-10(-26) × (2-)3-6(-9) µm. Sexual condition dioicous; male plants as large as females; interior perichaetial leaves abruptly acuminate, convolute-sheathing. Seta 0.5-1.5 cm, solitary, rarely 2 per perichaetium, yellowish to reddish brown. Capsule 1.2-2 mm, straight and erect to slightly inclined, rarely somewhat arcuate, smooth, striate when dry, light yellowish brown; operculum 1-1.5 mm. Spores 12-24 µm.

Dicranum montanum Hedw. Sp. Muse. 143. 1801
Dioicous: plants in dense cushions of usually a yellowish-green color; stems up to 4 cm. high, somewhat tomentose below: stem-leaves 3-4 mm. long, erect-spreading, when dry crispate, not secund, narrowly lanceolate, gradually and acutely long-pointed, grooved above rather than subtubulose, serrulate or crenulate one third down or more on the margins and the back of the costa; costa percurrent or shortly excurrent, one fourth to one fifth the width of the lower part of the leaf, in cross-section showing 4-6 guide-cells with stereid-bands above and below, of rather few and comparatively large cells, often not well differentiated ; alar cells brown or often pale, the cells in the blade just above elongate, those towards the costa often 8-10 times as long as broad, becoming gradually short-rectangular or nearly square in the upper half of the leaf, the cell-walls slightly thickened and not pitted; leaf -blade on the back from nearly smooth to quite densely cuamillose one half down the leaf; inner perichaetiat leaves strongly costate, rather loosely convolute, somewhat gradually narrowed to a rough point nearly as long as the broader part: seta up to 1.5 cm. long, either yellowish or reddish: capsule about 2 mm. long, cylindric, erect or slightly curved and nodding, when dry somewhat furrowed and contracted under the mouth, the exothecal cells with thin, somewhat sinuous walls mostly slightly thickened at the angles; annulus of two rows of pale cells; lid rostrate, two thirds the length of the capsule ; peristome-teeth red, vertically striate, divided often threefourths down : spores roughened, about 1 8 /j. in diameter.
Type locality: Germany.
Distribution: Newfoundland to West Virginia and westward to Manitoba and Minnesota, mostly on trunks and logs in mountains; Arizona; also in Europe and Asia.