Plants brown to black. Leaves erect-spreading, occasionally secund, broadly subulate from an ovate base, widest in proximal half of leaf, apex symmetric; costa present, percurrent and usually filling the leaf apices, moderately differentiated to strong, terete, reaching the leaf insertion; leaf margins entire or occasionally weakly crenulate; basal laminal cells quadrate to occasionally short-rectangular, marginal cells mostly quadrate or rounded, walls usually sinuose; medial laminal cells quadrate, 1-stratose to nearly completely 2-stratose, lumens rounded-quadrate; laminal papillae rare, low. Sexual condition clad- or gonioautoicous; perichaetial leaves differentiated, convolute-sheathing. Spores 35-60(-70) µm.
Siliceous rock, cliffs, boulders; low to high elevations; Greenland; B.C., N.B., Nfld. and Labr., N.S., Ont.; Ala., Alaska, Calif., Conn., Fla., Ga., Maine, Md., Mich., N.Y., N.C., Ohio, Oreg., Pa., Tenn., Vt., Va., Wash., W.Va.; n, c Europe.
H. A. Crum and L. E. Anderson (1981) did not recognize as Andreaea crassinervia those eastern North American specimens otherwise referable to A. rothii with excurrent or poorly defined costae (not bordered by laminal cells in the subula). B. M. Murray (1987) excluded A. crassinervia from the Arctic, while M. F. V. Corley et al. (1981) submerged it in A. rothii. The essentially European A. rothii var. falcata (Schimper) Lindberg (A. rothii var. papillosa Müller Hal.) is only poorly distinguished from the typical variety and does not warrant recognition here, at least on the basis of the single specimen reported for the flora area. The previously used traits of spore size and costa filling the acumen or not intergrade between those taxa.
Plants reddish black, black or greenish brown. Leaves curved or secund to straight, wide-spreading to squarrose, short-lanceolate, widest proximally, apex oblique or symmetric; costa absent; leaf margins entire; basal laminal cells short- to long-rectangular, marginal cells rounded-quadrate to short-rectangular, walls sometimes thickened, usually pitted, straight; medial laminal cells quadrate to short-rectangular, 1-stratose or occasionally 2-stratose in patches, lumens rounded, rectangular or irregularly stellate; laminal papillae usually present, commonly large, whitish. Sexual condition cladautoicous or autoicous; perichaetial leaves differentiated, convolute-sheathing. Spores 20-32(-50) µm.
Neutral to acidic boulders, cliffs and walls, generally wet sites; low to moderate elevations; Greenland; Nunavut, Que.; Alaska; nw Europe.
Andreaea rupestris is a species of many morphological variants, more commonly identified by simple elimination. It is similar to A. obovata, but is distinguished by the leaves generally curving or secund, short-lanceolate, widest proximally, apices oblique or symmetric. The degree of expression of laminal papillae is variable on the same plant. Plants identified as A. alpestris, said to differ by straight leaves with low papillae, is probably best considered a high elevation form.