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.)

The peculiar east-west disjunct distribution of Grimmia incurva in North America may reflect its preference for damp sites. Specimens have been collected in New England and in the Maritime Provinces, with a second widespread area running from the Yukon south through to California. It is uncommon in the continental interior. Grimmia incurva is a shade-loving subalpine species, characterized by rounded dark green cushions and linear, contorted leaves. The awns are visible only with a hand-lens. This species has a habit more like that of Dicranowesia crispula than of a Grimmia. H. A. Crum and L. E. Anderson (1981) reported immersed capsules, but that is not correct; they are clearly exserted (H. C. Greven 1995). Crum and Anderson also observed: “Specimens recorded from Maine can be considered a shade form of G. donniana.” However, this confusion extends beyond Maine. Greven renamed nearly all the G. donniana specimens from New York and New Hampshire in MICH to G. incurva. Hastings agrees that these specimens cannot be G. donniana because the leaf shape is virtually identical to that of G. incurva, being narrowly lanceolate and contorted. However, like G. donniana, and unlike G. incurva, the specimens are autoicous and the setae are straight. Rather than expanding the concept of either G. donniana or G. incurva to include these anomalous specimens, we propose that they represent an as yet unpublished species with a unique combination of characters. Hastings thus retains G. incurva as being dioicous and G. donniana as having oblong-lanceolate leaves.

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