Flora of North America species comparison

Grimmia ramondii occurs near sea level in arctic areas and along the West Coast. In the latter region, however, it is more common in mid-elevation montane sites and may also be found above the tree line. It differs from most Grimmia species by its lack of awns, winged costa, and tall, loose growth form. At first sight, G. ramondii has the habit of a Racomitrium. However, the sporophyte has an arcuate rather than straight seta, and the capsules are striate rather than smooth. Because of its habit and the absence of a central strand, K. G. Limpricht ([1885–]1890–1903, vol. 1) placed it, together with G. hartmanii and G. atrata, in Dryptodon, a genus intermediate between Grimmia and Racomitrium. There are many other Grimmia species, however, without a central strand, and G. hartmanii and G. atrata have already been removed from Dryptodon, so there is no reason to maintain that monotypic genus. Grimmia ramondii may be confused with G. hartmanii and G. elatior. However, the lack of awns, the Racomitrioideae-like areolation, and the distinct costal wings distinguish it easily from those species.

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

Grimmia longirostris is one of the most common species of the genus. It is most common in the eastern ranges of the Rocky Mountains, ranging from western Texas through the Canadian Rockies, and throughout much of Alaska. It is widely distributed in the Canadian sub-Arctic and Arctic, and is known from Greenland. With the exception of disjunct sites in Oklahoma and North Carolina, it is absent in the American Great Plains and Southeast. These latter areas are largely composed of calcareous rocks, a substrate avoided by G. longirostris. It is rare in coastal areas, becoming more common inland.

As Grimmia affinis, G. longirostris has commonly been placed as a subspecies of G. ovalis. Despite G. Sayre’s (1951) resolution of the differences between these taxa, a large proportion of specimens in major herbaria in North America that are named G. ovalis are actually G. longirostris. However, G. ovalis is dioicous and has leaves with plane margins that are broadly concave distally, usually with a distinct ovate base and well-defined shoulders. In contrast, G. longirostris is autoicous, and has leaves with one recurved margin, that are narrowly keeled distally, with a poorly defined basal region, often without a distinct shoulder. These characters clearly separate these two taxa at the specific level. Hastings puts G. longirostris into a group that also includes G. arizonae and G. pilifera. Grimmia longirostris is separated from those two species by non-sheathing leaf bases, usually long-exserted capsules, and cladautiocous sexuality. Grimmia longirostris is further separated from G. pilifera by having a stem with a distinct central strand and a thin epidermis, a costal transverse section that is typically reniform, and leaves that are recurved on only one margin. Rare specimens of G. longirostris with immersed capsules in the American Southwest may be almost indistinguishable from G. arizonae. In extremely xeric environments, specimens become friable and break into individual strands, making determination of the cladautiocous sexuality impossible. In these circumstances identification will always be uncertain. However, the leaves of G. longirostris are not sheathing; they are only loosely attached to the stem and usually can be peeled off intact. In contrast, the leaves of G. arizonae are sheathing and strongly attached to the stem; they often break at the base when trying to remove them. The costal transverse sections of G. longirostris are characteristically reniform (J. Muñoz 1998) while those of G. arizonae are usually semicircular. However, gradations from semicircular to reniform are not uncommon.

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