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 caespiticia is an uncommon species that occurs on siliceous rock outcrops above timberline in western North America. J. Muñoz (1998b) reported the species on dry rock, but H. C. Greven (1995) cited it as being hygrophytic. Hastings has observed specimens most commonly in moist areas, but occasionally also on dry rock. Grimmia caespiticia does not occupy sites as extreme as those of G. sessitana, being found at somewhat lower latitude and elevations. Except for a single site in New York state, it is not known from east of the front ranges of Colorado. Grimmia caespiticia and G. elongata are the only members of the Montanae group (in the sense of Muñoz) to be both dioicous and have stomata. Grimmia caespiticia typically has a cucullate leaf apex, a feature unknown in other members of the Montanae group and very rare in Grimmia. For most North American specimens, the cucullate apex is more easily seen than are the leaf plications. While usually present, the plications are often not evident except in transverse section. Eurasian specimens typically have, however, strongly developed plications. Most specimens of G. caespiticia have been misidentified as G. alpestris. These two species are similar in habit, have ovate leaves with incurved margins, may have bulging laminal cells, and are dioicous. However, G. caespiticia has stomata while G. alpestris has none. If a specimen has a cucullate leaf apex and/or the plications are well-developed in transverse section then it is most certainly G. caespiticia.

Grimmia caespiticia may also be confused with G. sessitana. These species are both found above timberline and both have bulging laminal cells and capsules with stomata. However, the incurved leaf margins, cucullate apex, and quadrate to short-rectangular basal areolation of G. caespiticia are quite different from the plane to recurved leaf margins with long-rectangular basal areolation typical of G. sessitana. Although the type specimen of G. alpestris var. holzingeri lacks capsules, gametophytically it is indistinguishable from muticous specimens of G. caespiticia. Specimens of var. holzingeri with capsules have been collected near the type locality and these specimens have stomata. Rather than accepting that G. alpestris may have stomata (in the sense of E. Lawton 1971), Hastings places var. holzingeri within the concept of G. caespiticia. In 1890, Kindberg described G. nivalis based on a specimen collected by J. Macoun at a high elevation site in southern British Columbia. This taxon is similar to G. caespiticia, differing mainly by having papillae on the leaf lamina. Having examined the type and other material of G. nivalis, Hastings interprets these features to be merely the remnants of laminal cell walls; the exterior surface of the strongly bulging cell wall has been worn away by the elements. H. C. Greven (2003) believed that the somewhat longer awns and weak plications of G. nivalis fit well with European specimens of G. pyrenaica, a taxon that has also been put in synonymy with G. caespiticia. Therefore, we place G. nivalis in synonymy with G. caespiticia.

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