Montana Field Guide

Plants: Growing in open to crowded clumps of upright shoots or tangled mats, green, pale yellow, occasionally tinged with grey or white above and appearing hoary, brown to black below. Stems mostly 2-4 cm in length, but occasionally up to 7, creeping to nearly upright, profusely laterally branched, many of the branches so short as to look like knobs (FNA 2007).

Leaves: Somewhat erect, overlapping, and frequently curved toward one side when dry, spreading a little when wet, 1.5-3.8 mm in length and 0.4-0.8 mm in width, lance-shaped, folded longitudinally above with a slender groove below; apex with a hair-point or rarely without, the hair-point hyaline, mostly 0.3-0.7 mm in length (sometimes longer) (FNA 2007), toothed, not papillose (Smith 1980); margins curved back and down for half or more the length of the leaf, seldom to the leaf tip; costa extending to the leaf tip, the dorsal surface rounded (FNA 2007).

Leaf Cells: Laminal cells smooth or frequently appearing papillose from longitudinal cuticular hills, unistratose; middle and upper cells oblong and very wavy, becoming wider than long toward the leaf edges; basal laminal cells long and narrow to linear, with thick, pitted walls; alar cells only slightly distinguished, if at all; margins of 1 cell layer, occasionally regions of 2 layers; basal marginal cells along the base in two rows, the cells square to short-oblong (seldom long), rarely wavy, seldom green with chlorophyll; costa in X-section from 2-3 cell-layers thick proximally, 2 cell-layers thick near the apex, and with 2-5 relatively large dorsal cells proximally transitioning to 1-3 dorsal cells near the apex (FNA 2007).

R. microcarpon differs from Racomitrium affine, R. heterostichum, and R. sudeticum in having well-developed basal borders (running up the leaf sides from the base), the cells of which are pellucid and not wavy. The other species do not have basal marginal borders or they are not well-defined (FNA 2007).

Acidophilic, mostly in moist to dry, open habitats; on large stones and bluffs, soil, areas of lingering snow, rocky inclines, granite (FNA 2007).

Dioicous. Inner perichaetial leaves prominently differentiated, hyaline below, green (chlorophyllous) above, seldom with a hair-point (FNA 2007).

Seta 2.5-8 mm tall, somewhat russet. Capsule mostly 1.2-2 mm in length, 0.3-0.6 mm in width, brown, a little shiny or not, exserted; operculum with a straight or oblique beak; peristome dentitions split almost to the base into 2 lobes or else long and narrowly perforate; somewhat red with yellow tones, papillate (FNA 2007).