Flora of North America species comparison

Grimmia ovalis is common and widespread in high elevation sites in western North America from southern British Columbia along the Rocky Mountain corridor to southern New Mexico and south central California. H. A. Crum and L. E. Anderson (1981) rejected all reports of G. ovalis from eastern North America. However, we have seen specimens from that area, although scattered and rare. It is not surprising that the species occurs in the eastern part of the continent given that it is widespread across the Laurasian continental plates and in India. Outlier sites in the Yukon and southern Greenland connect the North American populations to those in Asia and Europe, respectively. In western North America, G. ovalis is most often confused with G. longirostris and G. laevigata. While superficially similar to G. longirostris, G. ovalis has concave leaves with plane margins and is dioicous, while G. longirostris has keeled leaves with a recurved margin and is autoicous. Other points of separation are discussed under G. longirostris. Typical specimens of G. ovalis are readily separated from G. laevigata by their ovate-lanceolate leaves with a well-defined ovate base and narrowly attached awns. However, both of these species are variable in leaf shape, and while the awn of G. ovalis is usually narrowly attached, sometimes it is quite broad and may border on being decurrent. These specimens can be identified by the width of the costa and the basal areolation. Grimmia ovalis has a costa that is narrow at the base, while G. laevigata has a distinctly broad costa covering up to 1/3 of the base. The basal marginal cells of G. ovalis are most often short- to long-rectangular and hyaline while those of G. laevigata are always oblate to quadrate and not hyaline. In eastern North America, specimens of G. ovalis have been misidentified as G. olneyi. Aside from seta and capsule differences, G. ovalis has rectangular basal marginal laminal cells and its basal juxtacostal cells are long-rectangular to elongate; see also under G. olneyi.

Based on identifications by Greven, W. A. Weber et al. (2003) reported Grimmia bernoullii in the United States. That species differs from G. ovalis by its more ovate leaves without shoulders and with plane margins, costa broad at the base and disappearing in mid leaf, and sporophytically by its ellipsoid capsule with long-rostrate, straight operculum, and mitrate calyptra. Hastings has examined duplicate specimens from Missouri of those cited by Weber et al. and has determined that they do not deviate significantly from G. ovalis, having rather narrow leaves, costa narrow at the base and remaining strong in mid leaf, and with many leaves having incurved margins. The specimens were sterile and therefore sporophytic characters could not be determined. Based on these observations Hastings excludes G. bernoullii from the North American flora, although Greven would still retain the species.

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

Grimmia montana is widespread and common on acidic rock in the warm, dry, western interior of North America from southern British Columbia and Alberta southward to California and Colorado. It is very rare at higher latitudes, with outliers known from Alaska, southern Yukon, and northern British Columbia, and a few populations from Greenland and Baffin Island. It is not known from the interior Great Plains, which are largely calcareous. As reported by J. Muñoz (1998b), it is surprisingly absent from seemingly suitable sites in eastern North America. Because its leaf margins can be either plane and/or incurved, it is most commonly confused with G. donniana and G. alpestris, which have plane and incurved margins, respectively. Grimmia montana is readily separated from G. donniana because it is dioicous and lacks stomata, whereas G. donniana is autoicous and has stomata. Gametophytically, G. montana has quadrate to short-rectangular basal marginal laminal cells with thickened transverse walls, while G. donniana has long-rectangular cells with thin walls. Separating G. montana and G. alpestris can be difficult; they have broadly overlapping distributions and both are dioicous and lack stomata. Grimmia alpestris often has bulging, mammilose laminal cells that easily separate it from G. montana, but some stems have leaves that lack this feature. Specimens of G. montana can then be identified by their basal leaf areolation. The basal juxtacostal laminal cells of G. montana tend to be significantly longer than the marginal cells and the two regions are usually distinct. In contrast, G. alpestris tends to have a uniform basal areolation, composed of quadrate to short-rectangular cells.

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