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 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.)