Grimmia ovata var. affinis (Hornschuch) Bruch & Schimper
Plants in compact cushions, yellow green to dark olive green. Stems 1--3 cm, central strand strong. Stem leaves ovate-lanceolate, 1.5--3 × 0.6--0.7 mm, keeled, one margin recurved proximally, not sheathing, awn 0.5--1.5 mm, costal transverse section prominent; distal laminal cells 2-stratose, not bulging, marginal cells 2-stratose, not bulging; medial laminal cells short-rectangular, sinuose, thick-walled; basal juxtacostal laminal cells long-rectangular to linear, sinuose, thick-walled; basal marginal laminal cells short-rectangular, straight, thick transverse and thin lateral walls, hyaline. Perichaetial leaves not enlarged. Sexual condition cladautoicous. Seta straight, (1--)2--4 mm. Capsule usually present, (emergent to) exserted, yellow, oblong-ovoid to cylindric, exothecial cells short- to long-rectangular, thin-walled, stomates present in 2--3 rows, annulus of 2 rows, rectangular, thick-walled, operculum long-rostrate, peristome present, fully developed, split and perforate in distal half.
Exposed, dry, acidic granite and quartzite; 100--3050 m; Greenland; Alta., B.C., Labr., Man., N.B., Nfld., N.W.T, N.S., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Maine, Minn., Mont., Nev., N.Mex., N.C., Oreg, S. Dak., Tex., Utah, Vt., Wash., Wyo.; Mexico; Central America (Guatemala, Honduras, Costa Rica); South America; Eurasia; Africa; Pacific Islands; Australia.
Grimmia longirostris is one of the most common species of Grimmia. 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. It is absent in the American Great Plains and from the American Southeast, with the exception of a disjunct site in North Carolina. 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 Hornschuch, G. longirostris has commonly been placed as a subspecific entity of Grimmia 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. R.I. Hastings puts Grimmia longirostris into a group that also includes G. arizonae and G. pilifera. Grimmia longirostris is separated from these two species by non-sheathing leaf bases, usually long-exserted capsules, 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 Grimmia longirostris with immersed capsules in the American Southwest may be almost indistinguishable from G. arizonae. These specimens have been named Grimmia catalinensis Bartram. 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 Grimmia 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 1998a) while those of G. arizonae are usually terete. However, gradations from terete to reniform are not uncommon.