Montana Field Guide

Plants: Acrocarpous (Vitt 1988), growing in open clumps of upright shoots, sometimes sprinkled amongst other moss species, green, sometimes with a bluish bloom, in time turning brown. Stems 20-50 mm in height, regularly branching from just beneath terminal reproductive organs, often tree-like (FNA 2007), possessing a central strand (Lawton 1971).

Leaves: Upright, pressed near to the stem, and a little curved up and inward when dry, spreading broadly with the ends curved back and down when damp, dense and overlapping in the upper part of stems and branches, 2.5-6 mm in length, the sheathing base transparent and smooth along the edges and steadily tapering to or suddenly constricted at the limb (blade), the joint between sheath and limb distinct, the limb lance-shaped, widely to very slenderly so, weakly cupped, dentate from near the hinge to the leaf tip or nearly smooth; costa reaching or barely surpassing the apex, sometimes with a few teeth dorsally near the tip; lamellae green, covering most of the costa and lamina (FNA 2007).

Leaf Cells: Sheath-limb hinge consisting of thick-walled cells that reach up the limb margin slightly; lamellae 30-46, 4-7 cells in height, smooth along the top margin in side view, the uppermost lamellar cells large and heavily covered with papillae, in X-section wider than tall, the lumen somewhat pentagonal with the corners rounded; sheath cells short and quadrangular, becoming nearly isodiametric closer to the hinge; dorsal-facing cells nearly isodiametric with thick walls (FNA 2007)

Polytrichastrum alpinum, with its similar gametophyte, lacks the bluish bloom seen in P. urnigerum (Crum & Anderson et al., 1981).

Disturbed, coarsely-textured soil along streams or road margins, fissures of bluffs or stones, areas of lingering snow. From medium elevations (FNA 2007) ranging to about 6560 feet (Lawton 1971).

Dioicous. Perigonium cup-like (Lawton 1971). Seta smooth, usually solitary in a perichaetium, 10-40 mm in height. Capsule upright or tilted, pale brown to russet, in time turning very dark; 2-3 mm in length; peristome with 32 russet teeth with transparent edges (FNA 2007). Calyptra draping like a hood (Lawton 1971), covered with thickly matted hairs, shielding most or all of the capsule (FNA 2007).