Flora of North America species comparison

Of conservation concern.

Previous to its discovery in Iceland, as Grimmia grisea (H. C. Greven 1998), G. reflexidens was known from only the Southern Hemisphere. It had previously been collected east of East Bay, Newfoundland, now the only known locality in North America, but was not recognized as G. reflexidens. The latter is similar to G. asperitricha Dixon & Sainsbury of New Zealand, and the two species have been confused by G. O. K. Sainsbury (1945) as well as by R. Ochyra (1993). J. Muñoz (1998b) synonymized G. reflexidens with G. sessitana. However, the former is readily separated from the latter by: (1) enlarged perichaetial leaves, (2) decurrent awns, (3) non-bulging laminal cells, and (4) dioicous sexual condition. Capsules are unknown from Northern Hemisphere material, but G. reflexidens lacks stomata while they are present for G. sessitana. Although G. reflexidens and G. teretinervis both have decurrent awns they are easily separated by a number of characters: G. reflexidens grows in compact cushions, has long awns, and a semicircular costa; G. teretinervis grows in loose clumps, is hyaline-tipped to short-awned, and has a unique costa that is distally almost completely circular in transverse section.

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

Grimmia donniana is widespread but relatively uncommon and sporadic along the front ranges of the Rocky Mountains from Alberta south to southern Utah and Colorado. West of the Rockies it is known from a few locations in central Washington, northern Idaho, and northern Oregon. It is rare at higher latitudes, with a few records from Alaska, the Yukon, Northwest Territories, and Greenland. There are three disjunct populations in eastern North America: one in Michigan, one in the New England states and southern Quebec, and one in Labrador. Most specimens reported from British Columbia (R. R. Ireland et al. 1987) actually represent G. alpestris. Grimmia donniana is usually recognized by: (1) leaves with plane margins and (2) a hyaline rather uniform basal lamina with long-rectangular, thin-walled cells. The leaves of G. montana, while often incurved distally, may also have plane margins. The latter species, however, has quadrate to short-rectangular basal marginal cells that have thick end-walls and are rarely hyaline. It is also dioicous and lacks stomata. Grimmia sessitana can also have leaves with plane margins, but often one margin is recurved. Its basal marginal laminal cells are rectangular, like those of G. donniana, but they have thick rather than thin walls and are typically not hyaline. The leaf cells of G. sessitana are most often bulging, mammillose; those of G. donniana are not.

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