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 montana is widespread and common on acidic rock in the warm, dry, western interior of North America from southern British Columbia and Alberta southward to California and Colorado. It is very rare at higher latitudes, with outliers known from Alaska, southern Yukon, and northern British Columbia, and a few populations from Greenland and Baffin Island. It is not known from the interior Great Plains, which are largely calcareous. As reported by J. Muñoz (1998b), it is surprisingly absent from seemingly suitable sites in eastern North America. Because its leaf margins can be either plane and/or incurved, it is most commonly confused with G. donniana and G. alpestris, which have plane and incurved margins, respectively. Grimmia montana is readily separated from G. donniana because it is dioicous and lacks stomata, whereas G. donniana is autoicous and has stomata. Gametophytically, G. montana has quadrate to short-rectangular basal marginal laminal cells with thickened transverse walls, while G. donniana has long-rectangular cells with thin walls. Separating G. montana and G. alpestris can be difficult; they have broadly overlapping distributions and both are dioicous and lack stomata. Grimmia alpestris often has bulging, mammilose laminal cells that easily separate it from G. montana, but some stems have leaves that lack this feature. Specimens of G. montana can then be identified by their basal leaf areolation. The basal juxtacostal laminal cells of G. montana tend to be significantly longer than the marginal cells and the two regions are usually distinct. In contrast, G. alpestris tends to have a uniform basal areolation, composed of quadrate to short-rectangular cells.

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