Plants robust, ascending from a decumbent base, reddish. Stems 5--12 cm long, repeatedly dichotomous, central strand absent. Stem leaves loosely appressed when dry, patent to spreading when moist, towards the top of the stem becoming more and more secund, lanceolate to ovate-lanceolate, 3--4 × 0.6--0.9 mm, keeled, margins recurved on both sides, awns remotely denticulate, flattened below, widely decurrent, costa yellowish, ± 100 µm wide below, channeled distally; distal laminal cells 1-stratose, margins partly 2-stratose; medial laminal cells rectangular, nodulose, thin oblique transverse walls and extremely thick lateral walls; basal juxtacostal laminal cells elongate, ± porose, thick-walled; basal marginal laminal cells in a few rows short-rectangular, thick-walled. Gemmae absent. Sexual condition dioicous. Seta arcuate, 3--4 mm. Capsule occasionally present, exserted, yellowish-green, obloid, striate, exothecial cells rather thick-walled, annulus present, operculum rostrate, peristome teeth orange to reddish, perforated, irregularly cleft at apex, nearly smooth below, papillose. Calyptra mitrate.

Dry acidic boulders; 500--1500 m; B.C.; Calif., Idaho, Mont., Oreg.

The western North American endemic, Grimmia leibergii has the habit of Racomitrium heterostichum (Hedw.) Brid., and nearly all specimens of this species in NY, and probably also in other North American herbaria, have been stored as varieties of that species. This confusion is probably the reason why G. leibergii has not been recognized in the United States. J. B. Leiberg (1893) stated that it was most closely related to G. decipiens, a species that does not occur in North America. Both taxa share robust gametophytes, striate capsules on arcuate setae with long, straight opercula, broadly ovate-lanceolate leaves with recurved margins and rectangular mid leaf cells with extremely thick and nodulose lateral walls and thin transverse walls. However, G. decipiens is autoicous, it is a much smaller species, with sharply denticulate awns that, although sometimes flattened basally, are only very shortly decurrent; the gametophytes form comal tufts, so the distal leaves are 2--3 times longer than the lower leaves, and are not secund.