Flora of North America species comparison

In North America, Grimmia trichophylla is principally a lowland species, occurring in the mountains up to about 1000 m., rarely higher. In the Southern Hemisphere, it may be found up to 4000 m. In New Zealand, the species is common, and in contrast to G. trichophylla in North America, frequently bears capsules. The New Zealand plants are usually smaller than American specimens, and the leaves are frequently contorted. The nearly cosmopolitan G. trichophylla has many phenotypes, and numerous subspecies and varieties have been described. In damp and shaded habitats, the awns may be short, just as in dry unfavorable habitats at high altitudes, where stunted specimens may occur with small, short leaves and reduced awns, or even with muticous leaves. Grimmia trichophylla has frequently been confused with related species such as 36. G. muehlenbeckii and 34. G. lisae (see discussions thereunder for identification details). Robust forms of G. trichophylla have been mistaken for G. austrofunalis (H. C. Greven 1997, 2003), which does not occur in North America. Although some of those plants have leaves of equal length along the stem, characteristic of G. austrofunalis, they also have both leaf margins recurved, and the medial and outer basal laminal cells are longer and more robust than in that species.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Grimmia donniana is widespread but relatively uncommon and sporadic along the front ranges of the Rocky Mountains from Alberta south to southern Utah and Colorado. West of the Rockies it is known from a few locations in central Washington, northern Idaho, and northern Oregon. It is rare at higher latitudes, with a few records from Alaska, the Yukon, Northwest Territories, and Greenland. There are three disjunct populations in eastern North America: one in Michigan, one in the New England states and southern Quebec, and one in Labrador. Most specimens reported from British Columbia (R. R. Ireland et al. 1987) actually represent G. alpestris. Grimmia donniana is usually recognized by: (1) leaves with plane margins and (2) a hyaline rather uniform basal lamina with long-rectangular, thin-walled cells. The leaves of G. montana, while often incurved distally, may also have plane margins. The latter species, however, has quadrate to short-rectangular basal marginal cells that have thick end-walls and are rarely hyaline. It is also dioicous and lacks stomata. Grimmia sessitana can also have leaves with plane margins, but often one margin is recurved. Its basal marginal laminal cells are rectangular, like those of G. donniana, but they have thick rather than thin walls and are typically not hyaline. The leaf cells of G. sessitana are most often bulging, mammillose; those of G. donniana are not.

(Discussion copyrighted by Flora of North America; reprinted with permission.)