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 mollis, discovered by Schimper in the Tirol of Austria, is a characteristic arctic-alpine species, frequently growing in glacial streams, sometimes over reaches of hundreds of meters. Although the species is widespread in the Northern Hemisphere, it is nowhere common. It occurs exclusively above the treeline. Because of its unique subpercurrent costa, uniform lamina of quadrate, thin-walled cells, and peculiar ecological niche, it cannot easily be confused with any other species. I. Hagen (1909) placed it in a monotypic genus, Hydrogrimmia. This concept was followed by M. F. V. Corley et al. (1981). However, there are no significant morphological characters to separate it from Grimmia, prompting H. C. Greven (2003) to follow, in agreement with H. A. Crum and L. E. Anderson (1981), Bruch and Schimper’s original concept. This dioicous species grows in separate male and female cushions, and capsules are produced very rarely.

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