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 laevigata is widespread and relatively common on the southern Great Plains, into the Ozarks, and along the Appalachians from northeastern Alabama to New England. There is also an extensive outlier in southern Minnesota and adjacent states. In western North America, it is abundant in California and the Pacific Northwest region into south central British Columbia. Although it occurs in the Rocky Mountain region it is not common there, being found mostly in lower elevation sites and along the east slopes. With the exception of a few disjunct sites in southern Georgia and Florida, it is unknown from the coastal plains of the American southeast. This is probably related to the extensive cover of calcareous Cretaceous and more recent bedrock. The northern limit of G. laevigata suggests a distribution influenced by the winter position of the Arctic airmass. Although known from high elevations, it is most often found below treeline on granite and acidic sandstones. It is an early successional invader of granitic rocks in the southeastern piedmont (H. J. Oosting and L. E. Anderson 1937, 1939; C. Keever et al. 1951). Classic specimens of G. laevigata are recognized by their broad leaves with almost no shoulder separating the proximal and distal lamina, and by their robust, broadly attached and long-decurrent awns. However, G. laevigata is quite variable with respect to leaf shape and awn attachment, with some specimens having bases approaching ovate and then often with rather narrowly attached awns. These specimens may be assigned to G. laevigata by the wide costa and oblate to quadrate basal marginal cells. Sterile specimens may be separated from G. crinitoleucophaea by the wide costa and thick-walled basal cells.

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