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 olneyi is endemic to eastern North America, with its center of distribution along the Appalachians from the New England states to North Carolina and eastern Tennessee. A disjunct population occurs on the Ozark Plateau of Missouri and Arkansas. Unlike G. unicolor, G. olneyi is tolerant of calcareous rocks and is able to occupy drier sites. Because of its sigmoid seta and somewhat wrinkled capsule, it is usually placed in subg. Rhabdogrimmia. However, the seta of G. olneyi is usually only somewhat sigmoid and is rarely arcuate. Further, its capsules only become wrinkled when dry, whereas the members of subg. Rhabdogrimmia typically have plicate capsules whether dry or turgid. In fact, specimens of G. olneyi are most commonly misidentified as either G. ovalis or G. laevigata, in subg. Litoneuron. The seta and capsule of G. olneyi are at the extremes of both subgenera. However, the general habit of the plants and their leaf structure suggests a close relationship with G. ovalis and G. unicolor.

Grimmia olneyi and G. laevigata have broadly overlapping distributions in eastern North America, where many specimens of G. olneyi have been misidentified as G. laevigata. Typical specimens of G. olneyi are readily separated from G. laevigata. However, some leaves on a stem of G. laevigata may have defined ovate bases with narrowly decurrent awns. These specimens will resemble G. olneyi. However, the costa of G. olneyi is always narrow at the base, while that of G. laevigata becomes broad at the base, occupying up to 1/3 of the lamina, and the costa grades gradually into the basal laminal cells. Furthermore, G. olneyi has quadrate to short-rectangular basal juxtacostal cells, while those of G. laevigata are elongate, almost resembling costal cells. Grimmia olneyi most closely resembles G. ovalis. Both have ovate lanceolate leaves from an ovate base, with a narrow distal lamina that is channelled, ending in a narrowly attached, long and toothed awn. The costa is narrow proximally in both species. However, they are otherwise quite distinct. Aside from the sigmoid seta and slightly wrinkled dry capsule of G. olneyi, its basal juxtacostal laminal cells are shorter and straighter than those of G. ovalis and its basal marginal cells are quadrate while those of G. ovalis are mostly rectangular. Geographical distribution has also been used to separate these species; H. A. Crum and L. E. Anderson (1981) rejected all reports of G. ovalis from eastern North America. However, we have seen a number of specimens of it from there and conclude that geography alone is not a reliable basis on which to differentiate these species.

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