Authors: Roxanne I. Hastings & Dr. Henk C. Greven

Plants in ascending, dichotomously branched patches, green. Stems 2--8 cm, central strand absent. Stem leaves slightly contorted with often secund apices when dry, distal leaves usually falcato-secund when moist, broadly lanceolate, tapering to an acuminate apex, 2.5--4.5 × 0.4--0.6 mm, keeled, margins usually recurved on one side, awns very short, denticulate, costa firm, projecting on dorsal side; distal laminal cells 1-stratose, margins 2-stratose; medial laminal cells quadrate to short-rectangular, slightly sinuouse, thick-walled; basal juxtacostal laminal cells linear, slightly sinuose, thick-walled; basal marginal laminal cells quadrate, thickened transverse walls. Gemmae in clusters, mulberry-shaped, brown, borne on leaf apices, usually present. Sexual condition dioicous. [Seta straight to flexuose, 3--4 mm. Capsule extremely rare, exserted, yellowish-green, clavate-obloid, smooth, exothecial cells thick-walled, annulus present, operculum rostrate, peristome teeth orange, deeply split, perforated distally, papillose. Calyptra mitrate.]

Shaded boulders, especially granite, in woodlands; 100--1500 m; P.E.I., Que.; Utah; Eurasia; n Africa.

Grimmia hartmanii is principally a lowland species, occurring in the mountains up to 1500 m. With the separation of G. anomala from this taxon, G. hartmanii is much less common in North America than was previously thought. It is known principally from the Northeast. Although it is found usually in densely shaded habitats, in areas with high humidity it can establish itself in exposed habitats. Grimmia hartmanii resembles more closely some species of Racomitrium than those of its own genus, but it may be recognized by the usually spreading falcato-secund distal leaves, the very small awns and the terminal clusters of brown gemmae, which are conspicuous and usually present. Capsules are extremely rare and are unknown in North America.