Montana Field Guide

Plants: Somewhat thin but stiff, in open or crowded tufts or broad mats, frequently grey-tipped, greyish-green (FNA 2007) to yellow-green above (Smith 1978), dark brown or black below. Main stems mostly prostrate (Smith 1978) or ascending, 2-6 cm in height (sometimes up to 12 cm), with few to many branches ascending or short and upright (Smith 1978).

Leaves: Appressed, rotated or curving to the side when dry, erect-spreading when wet, lance-shaped (FNA 2007) from a wider basal part (Smith 1978), 2-4.7 mm in length (including awn), 0.6-0.9 mm in width, unistratose throughout; margins curved down and back distally, sometimes moreso on one side than the other, unistratose throughout with a few bistratose points distally; apex with a pronounced, mostly long 0.5-1.5(-3) mm, colorless awn, the awn frequently decurrent, and clearly toothed on its margins, a little crinkled and bearing tiny teeth abaxially; costa extending to or not quite to the apex, forming a channel on the inside of the leaf and a faint convexity on the outside, with 3-4 cell layers near the leaf base, 2 (sometimes 3) layers at the middle, and 2 layers above (FNA 2007).

Leaf Cells: Basal cells narrow and long with wavy, knobby thick walls; alar cells not or only a little distinct, yellowish; the outer alar cells not distinct; medial and distal cells nearly square or elongated (FNA 2007), extremely wavy (Smith 1978), becoming wider than long near the margins above (FNA 2007).

Racomitrium heterostichum is closely related to and apt to be confused with Bucklandiella affinis. However, the channeled costa of R. heterostichum is (most often) bistratose in the middle and just above, and weakly ridged on the back side of the leaf. The costa of B. affinis is 3-stratose in those same areas and is prominently ridged on the back side (FNA 2007).

Bucklandiella sudetica is also similar but has shorter awns. Its awns are 0.15-0.4 mm in length whereas B. heterostichum has awns ranging from 0.5-1.5(-3) mm (FNA 2007).

Dry and exposed acidic rocks and cliffs (Elliott 2016; FNA 2007), occasionally shady moist places. Low to high elevations (FNA 2007).

Innermost perichaetial bracts colorless, lacking hairs, and with a dull point. Seta straight or curved (Smith 1978), 4-9 mm in length, brown. Capsule 1.5-3.0 mm in length, slightly glossy brown, short cylindric (FNA 2007) to narrowly ellipsoid; operculum with a long beak (Smith 1978); peristome teeth ochre and papillate (FNA 2007).