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 alpestris has a distribution similar to that of G. montana, being widespread and common on acidic rock in the warm, dry, western interior of North America from southern British Columbia and Alberta to California and Colorado. The other two North American species with bulging laminal cells, G. caespiticia and G. sessitana, both have capsules with stomata, readily separating capsulate specimens from G. alpestris. H. C. Greven (2003) reported that the capsules of G. alpestris are brown, with thick exothecial cell walls, and are smooth when empty, whereas those of G. sessitana are yellowish to light brown, with thin-walled exothecial cells, and are striolate when empty. The incurved margins and uniformly 2-stratose distal lamina of G. alpestris contrasts with the plane or one recurved margin and 1-stratose distal juxtacostal laminal cells of G. sessitana. The dioicous sexuality of G. alpestris also helps to separate these species. Some specimens of G. alpestris have leaves with streaks of thickened or multistratose cells; superficially these may appear to be plications. However, in transverse section they are readily separated from the truly plicate leaves of G. caespiticia. Furthermore, G. alpestris leaves are never cucullate, while those of G. caespiticia usually are. Grimmia alpestris is best separated from G. montana by its often bulging laminal cells and secondarily by its relatively uniform, quadrate to short-rectangular basal areolation. While G. donniana also has a uniform basal areolation, its cells are much longer and thin-walled, and its margins are plane throughout the length of the leaf.

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