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.)

Of conservation concern.

Grimmia brittoniae is an endemic of western Montana and northern Idaho. It was described by Williams based on a set of specimens that he collected near Columbia Falls. It grows in warm, dry but climatically moist valley-bottom or piedmont forests dominated by Douglas fir. It is distinctive and easily recognized in the field. The often extensive cushions found on rocky underhangs are a characteristic blue-green color when moist, cracking into polygonal patterns when dry. The extremely long awns at once separate it from all other species of the genus. Grimmia brittoniae can be confused only with small forms of G. funalis, which also may grow in compact hoary cushions that are glaucous green in the distal part and brown inside. J. Muñoz (2000) synonymized G. brittoniae with that species. H. C. Greven and T. Spribille (1999), however, had already demonstrated that in G. funalis the leaves are usually spirally curved, the distal areolation is 2-stratose, the proximal leaves are blackish with short awns, the margins are plane or recurved on one side, and the basal cells are linear, thick-walled, and sinuose. In addition, G. funalis is characterized by male plants growing in separate cushions, with muticous to very short-awned leaves. Male plants of G. brittoniae grow intermingled with female ones and can hardly be separated from them. Grimmia brittoniae is more closely related to G. orbicularis. The leaves of both species are similar. However, the awns of the latter are much shorter, it is autoicous, usually with capsules on arcuate setae, the peristome teeth are broad, cribrose, and irregularly cleft at the apex, and the operculum is mammillate. Although Williams originally described G. brittoniae as having concave leaves with plane, sometimes 2-stratose margins, the leaves are keeled distally, and the margins are narrowly recurved and only very rarely 2-stratose. The recurved margins, however, are only present in leaves still attached to the stems; once detached and pressed under a cover glass, the margins appear plane.

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