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 caespiticia is an uncommon species that occurs on siliceous rock outcrops above timberline in western North America. J. Muñoz (1998b) reported the species on dry rock, but H. C. Greven (1995) cited it as being hygrophytic. Hastings has observed specimens most commonly in moist areas, but occasionally also on dry rock. Grimmia caespiticia does not occupy sites as extreme as those of G. sessitana, being found at somewhat lower latitude and elevations. Except for a single site in New York state, it is not known from east of the front ranges of Colorado. Grimmia caespiticia and G. elongata are the only members of the Montanae group (in the sense of Muñoz) to be both dioicous and have stomata. Grimmia caespiticia typically has a cucullate leaf apex, a feature unknown in other members of the Montanae group and very rare in Grimmia. For most North American specimens, the cucullate apex is more easily seen than are the leaf plications. While usually present, the plications are often not evident except in transverse section. Eurasian specimens typically have, however, strongly developed plications. Most specimens of G. caespiticia have been misidentified as G. alpestris. These two species are similar in habit, have ovate leaves with incurved margins, may have bulging laminal cells, and are dioicous. However, G. caespiticia has stomata while G. alpestris has none. If a specimen has a cucullate leaf apex and/or the plications are well-developed in transverse section then it is most certainly G. caespiticia.

Grimmia caespiticia may also be confused with G. sessitana. These species are both found above timberline and both have bulging laminal cells and capsules with stomata. However, the incurved leaf margins, cucullate apex, and quadrate to short-rectangular basal areolation of G. caespiticia are quite different from the plane to recurved leaf margins with long-rectangular basal areolation typical of G. sessitana. Although the type specimen of G. alpestris var. holzingeri lacks capsules, gametophytically it is indistinguishable from muticous specimens of G. caespiticia. Specimens of var. holzingeri with capsules have been collected near the type locality and these specimens have stomata. Rather than accepting that G. alpestris may have stomata (in the sense of E. Lawton 1971), Hastings places var. holzingeri within the concept of G. caespiticia. In 1890, Kindberg described G. nivalis based on a specimen collected by J. Macoun at a high elevation site in southern British Columbia. This taxon is similar to G. caespiticia, differing mainly by having papillae on the leaf lamina. Having examined the type and other material of G. nivalis, Hastings interprets these features to be merely the remnants of laminal cell walls; the exterior surface of the strongly bulging cell wall has been worn away by the elements. H. C. Greven (2003) believed that the somewhat longer awns and weak plications of G. nivalis fit well with European specimens of G. pyrenaica, a taxon that has also been put in synonymy with G. caespiticia. Therefore, we place G. nivalis in synonymy with G. caespiticia.

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