Taxon	Illustrator ⠉
	Grimmia americana	Patricia M. Eckel
	Grimmia atrata	Patricia M. Eckel
	Grimmia attenuata	Patricia M. Eckel
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Plants 5–40 (–70) mm, in dense cushions to loose mats, olivaceous, dark black-green to rusty-redbrown. Leaves broadly oblong-ovate, oblong-lanceolate, to narrowly ovatelanceolate, rarely ligulate, concave or keeled distally, margins plane, incurved or recurved, distal lamina 1-stratose to multistratose, specialized laminal and marginal chlorophyllose structures absent, muticous to long-awned but awns only rarely longer than lamina; basal-cells oblate to elongate, with straight or sinuose and thin to thick cell-walls; mid leaf and distal cells quadrate to rectangular, usually sinuose and thick-walled. Gemmae present or absent. Sexual condition autoicous or dioicous; perichaetial leaves enlarged or not. Seta short to long, straight, arcuate, or rarely sigmoid. Capsule erect, rarely pendent, immersed to long exserted, symmetric or rarely ventricose (subg. Grimmia), ovoid to obloid, rarely globose or cylindric; annulus poorly differentiated or well-defined comprised of quadrate, thin-walled or quadrate to rectangular, thick-walled cells; operculum mammillate, conic, or rostrate, falling detached from the columella. Calyptra mitrate or cucullate, not erose, small to medium, usually covering 1/2 or less of capsule, sometimes just covering operculum, smooth.

Distribution

North America, Mexico, Central America, South America, Eurasia, Africa, Pacific Islands, Australia, Antarctic

Discussion

Species 95 (43 in the flora).

The genus Grimmia is found on all continents. However, nearly half (44) of the species are endemics and have restricted distributions. Most species of Grimmia prefer dry and temperate or cold environments—there is no species only known from tropical areas. Nearly all species of Grimmia are saxicolous with a marked preference for acidic bedrock. Only the subgenus Grimmia prefers calcareous rock, with a few other species in other subgenera characteristic of neutral to basic substrates.

Hastings has attempted to place species in the subgenera Grimmia, Guembelia, and Litoneuron into groups of related or similar-looking ones. Because of the diversity within subg. Rhabdogrimmia, Greven felt it most convenient to present this group largely in alphabetical order. While the proper subdivision of Grimmia remains uncertain, both authors agree that for purposes of identification, the present division is best for this very complicated genus. Hastings authored the accounts for species 1–8, 10, 11, 13–16, 18, and 20–24, Greven those for species 10, 13, 18, 20, 25–43. Both authors together wrote the entire key.

Selected References

Greven, H. C. 1999. A synopsis of Grimmia in Mexico, including Grimmia mexicana, sp. nov. Bryologist 102: 426–436.

Greven, H. C. 2003. Grimmias of the World. Leiden.

Sayre, G. 1952. Key to the species of Grimmia in North America. Bryologist 55: 251–259.

Lower Taxa

Grimmia subg. Grimmia, Grimmia subg. Guembelia, Grimmia subg. Litoneuron, Grimmia subg. Rhabdogrimmia, Grimmia subg. Undetermined

Key

1	Costa ending well before the apex; leaf tip rounded to cucullate, muticous; lamina uniformly 1-stratose; laminal cells all quadrate.	Grimmia mollis
1	Costa reaching apex; leaf tip rounded to acute, muticous or awned; lamina usually with 2-stratose areas towards margins or with 2-stratose ridges; laminal cells oblate, quadrate, rectangular or elongate	> 2
2	Seta eccentrically attached to capsule base; capsule immersed, smooth, ventricose; stomata 3-4, large, at base of capsule (subg. Grimmia)	> 3
2	Seta centrally attached to capsule base; capsule immersed to exserted, smooth to plicate, not ventricose; stomata none to many, small, at neck to base of capsule	> 6
3	Distal leaves concave-keeled; distal lamina 1-stratose or with 2-stratose patches, margins 1- or 2-stratose; annulus absent or reduced to 1-2 rows of small cells; operculum mammillate	> 4
3	Distal leaves concave; distal lamina 2-stratose with 2-stratose margins; annulus prominent; operculum rostrate	> 5
4	Peristome present, annulus absent; distal lamina 1-stratose, margins 1- or 2- stratose	Grimmia plagiopodia
4	Peristome absent, annulus present; distal lamina 1-stratose with 2-stratose patches, margins 2-stratose.	Grimmia anodon
5	Basal laminal cells thick-walled; gonioautoicous; peristome fully developed.	Grimmia americana
5	Basal laminal cells thin-walled; dioicous; peristome rudimentary.	Grimmia crinitoleucophaea
6	Leaves merely 1-stratose distally; margins at most narrowly 2-stratose; one or both leaf margins recurved (G. reflexidens plane) (mostly subg. Rhabdogrimmia)	> 7
6	Leaves 2-3-stratose distally or 1-stratose with distal margins widely 2-stratose (G. sessitana and some G. donniana); leaf margins incurved, plane or recurved	> 26
7	Costa projecting on abaxial side with two wings.	Grimmia ramondii
7	Costa on abaxial side smooth or angled	> 8
8	Leaves muticous, without awns or only distal leaves with very short awn or hyaline tip	> 9
8	At least distal or perichaetial leaves with distinct awns	> 13
9	Leaves cucullate.	Grimmia atrata
9	Leaves not cucullate	> 10
10	Leaves squarrose when moist; medial laminal cells oblate to rounded quadrate	Grimmia lisae
10	Leaves erect to patent when moist; medial laminal cells quadrate to short-rectangular	> 11
11	Basal marginal cells with thickened transverse walls; seta arcuate; globular gemmae occasionally present on leaves.	Grimmia trichophylla
11	Basal marginal cells with thin transverse walls; seta straight or slightly arcuate; gemmae absent	> 12
12	One leaf margin recurved; medial laminal cells sinuose; seta straight or slightly arcuate	Grimmia elongata
12	Leaf margins both recurved; medial laminal cells with nodulose walls; seta straight.	Grimmia lesherae
13	Awns nearly equal to or much longer than lamina, decurrent, seta straight to flexuose	> 14
13	Awns typically shorter than lamina (G. pulvinata can be long); decurrent or not; seta arcuate to cygneous	> 15
14	Awns 1-2 mm, leaf margins plane, [seta straight]; only known from Maritime provinces in North America.	Grimmia reflexidens
14	Awns 2-4 mm, leaf margins both recurved; seta flexuose; endemic to Montana and Idaho.	Grimmia brittoniae
15	Leaves abruptly narrowed to awns, apex rounded; autoicous	> 16
15	Leaves gradually tapering to awns, apex narrowed; dioicous	> 18
16	Operculum rostrate; basal marginal laminal cells quadrate to short-rectangular	Grimmia pulvinata
16	Operculum mammillate to conical; basal marginal laminal cells short- to long-rectangular	> 17
17	Awns only on perichaetial leaves; basal juxtacostal cells with thin, straight walls; marginal distal lamina 2-stratose; acidic rocks.	Grimmia moxleyi
17	Awns on all distal leaves; basal juxtacostal cells with thick, nodulose walls; marginal distal lamina 1-stratose; basic rocks.	Grimmia orbicularis
18	Clusters of gemmae easily visible on abaxial side of leaf lamina or on leaf tips	> 19
18	Clusters of gemmae absent or in obscure clusters in leaf axils	> 21
19	Multicellalar gemmae on abaxial side of leaf lamina in distal leaves; leaves crisped and contored.	Grimmia torquata
19	Cluster of gemmae only on leaf tips; leaves straight	> 20
20	Leaves with blunt eroded apices; distal cells with pseudo- papillose walls; stem central strand present.	Grimmia anomala
20	Leaves with acuminate apices; distal cells with smooth walls; stem central strand absent.	Grimmia hartmanii
21	Leaves narrowly ovate-lanceolate to linear-lanceolate, distinctly incurved or contorted when dry.	Grimmia incurva
21	Leaves lanceolate to ovate-lanceolate, straight, appressed, only occasionally somewhat contorted when dry	> 22
22	Central strand absent; basal juxtacostal leaf cells uniformly elongate to linear, strongly nodulose and thick-walled; mid leaf cells extremely sinuose and very thick-walled; leaf margins both recurved	> 23
22	Central strand present; basal juxtacostal cells short- to long-rectangular, elongate cells absent or few and scattered; mid leaf cells straight to sinuose, thin- to thick-walled; leaf margins one or both recurved	> 24
23	Costa circular, projecting in transverse section; basal marginal cells thin-walled; distal leaves straight, awns not decurrent.	Grimmia attenuata
23	Costa semicircular, not projecting in transverse section; basal marginal cells thick-walled; distal leaves often secund, awns often decurrent	Grimmia leibergii
24	Leaves squarrose when moist; mid leaf cells rounded to oblate, straight.	Grimmia lisae
24	Leaves erect to patent when moist; mid leaf cells rounded-quadrate to short-rectangular, sinuose	> 25
25	Blackish green tufts; costa angled or bluntly winged in transverse section; awns denticulate, occasionally decurrent; capsule globose, brown.	Grimmia muehlenbeckii
25	Yellowish green tufts; costa semicircular in transverse section; awns smooth to slightly denticulate, not decurrent; capsule oblong-ovoid, yellow-green	Grimmia trichophylla
26	Leaves concave; costa not prominent; margins plane or incurved; dioicous (subg. Litoneuron)	> 27
26	Leaves keeled; costa prominent; margins recurved, plane or incurved; autiocous or dioicous (mostly subg. Guembelia)	> 33
27	All leaves muticous, straight or falcate	> 28
27	At least distal leaves awned, straight	> 29
28	Leaves oblong-lanceolate to ligulate, straight, cucullate, obtuse-rounded; basal marginal laminal cells short-rectangular; widely distributed.	Grimmia unicolor
28	Leaves oblong-lanceolate, homomallous-falcate, subulate, uncinate; basal marginal laminal cells quadrate to short-rectangular; endemic to Pacific Coast region.	Grimmia hamulosa
29	Leaves oblong-ovate to oblong-lanceolate; basal marginal laminal cells oblate to quadrate; costa broad at base; awn broadly attached and decurrent.	Grimmia laevigata
29	Leaves ovate-lanceolate from an ovate base; basal marginal laminal cells quadrate to long-rectangular; costa narrow at base; awn typically narrowly attached and not decurrent	> 30
30	Costa-like multistratose leaf bands present in transverse section.	Grimmia serrana
30	Costa-like multistratose leaf bands absent	> 31
31	Capsule emergent, gymnostomous, stomata absent, operculum mammilate; basal laminal cells uniformly short-rectangular, straight and thin-walled.	Grimmia nevadensis
31	Capsule exserted, peristome fully developed, stomata present, operculum rostrate; basal marginal and juxtacostal laminal cells typically contrasting in length or thickness	> 32
32	Basal marginal laminal cells quadrate; basal juxtacostal laminal cells quadrate to short-rectangular; seta sigmoid; capsule wrinkled when dry; perichaetial leaves not enlarged; endemic to eastern North America.	Grimmia olneyi
32	Basal marginal laminal cells quadrate to long-rectangular; basal juxtacostal laminal cells rectangular to elongate; seta straight; capsule smooth when dry; perichaetial leaves enlarged; widely distributed.	Grimmia ovalis
33	Margins plane or incurved	> 34
33	Margins recurved on one or both sides	> 44
34	Costa transverse section circular distally; awn hyaline-tipped to short (0.3 mm), decurrent	Grimmia teretinervis
34	Costa transverse section semicircular distally; awn short to long, usually prominent, decurrent or not	> 35
35	Seta arcuate; leaves spirally curved around stem when dry, flagelliform innovations present	Grimmia funalis
35	Seta straight; leaves straight when dry, flagelliform innovations absent	> 36
36	Gemmae abundant on adaxial distal leaf surface.	Grimmia shastae
36	Gemmae absent on leaves	> 37
37	Distal laminal cells bulging	> 38
37	Distal laminal cells not bulging	> 40
38	Leaf margins plane; cladautoicous; basal juxtacostal laminal cells rectangular to elongate; distal juxtacostal laminal cells 1-stratose; stomata present.	Grimmia sessitana
38	Leaf margins incurved; dioicous; basal juxtacostal laminal cells quadrate to short-rectangular; distal juxtacostal laminal cells 2-stratose; stomata present or absent	> 39
39	Stomata absent; leaves not plicate, not cucullate.	Grimmia alpestris
39	Stomata present; leaves weakly to rarely strongly plicate distally, cucullate	Grimmia caespiticia
40	Margins plane throughout; basal marginal laminal cells short- to long-rectangular; stomata present; autoicous	> 41
40	Margins incurved distally; basal marginal laminal cells quadrate to short-rectangular; stomata absent; dioicous	> 42
41	Distal juxtaxcostal laminal cells 2-stratose, occasionally 1-stratose; basal marginal leaf cells long-rectangular, hyaline; annulus large, of 2 rows of rectangular cells, revoluble; calyptra mitrate.	Grimmia donniana
41	Distal juxtacostal laminal cells 1-stratose; basal marginal leaf cells short- to long-rectangular, rarely hyaline; annulus small, of 1 row of quadrate cells, not revoluble; calyptra cucullate.	Grimmia sessitana
42	Capsule immersed to emergent, wide-mouthed, peristome rudimentary; endemic to California.	Grimmia mariniana
42	Capsule exserted, narrow-mouthed, peristome present, fully developed; widespread in western North America	> 43
43	Basal juxtacostal laminal cells short- to long-rectangular, distinct from quadrate to short-rectangular basal marginal cells; medial laminal cells rounded, thick-walled.	Grimmia montana
43	Basal juxtacostal and marginal cells quadrate to short-rectangular, basal areolation relatively uniform; medial laminal cells quadrate to short-rectangular, thin-walled.	Grimmia alpestris
44	Leaves muticous, cucullate.	Grimmia atrata
44	Leaves awned, not cucullate	> 45
45	Leaves spirally curved around stem when dry, flagelliform innovations present.	Grimmia funalis
45	Leaves straight when dry, flagelliform innovations absent	> 46
46	Sporophytes present	> 47
46	Sporophytes absent	> 51
47	Capsule immersed	> 48
47	Capsule exserted	> 49
48	Stem central strand present, epidermis thin; leaf margins 2-stratose, not thickened, one margin recurved (rarely both); leaves broadly ovate- lanceolate.	Grimmia arizonae
48	Stem central strand absent, epidermis thick; leaf margins 3(-4) stratose, thicker than juxtacostal lamina, usually both margins recurved; leaves narrowly lanceolate from an ovate base.	Grimmia pilifera
49	Seta arcuate; dioicous.	Grimmia elatior
49	Seta straight; autoicous	> 50
50	Annulus small, 1 row of quadrate cells; stomata in 1 row; basal juxtacostal cells straight and thin-walled.	Grimmia sessitana
50	Annulus prominent, 2 rows of rectangular cells; stomata in 2-3 rows; basal juxtacostal cells sinuose and thick walled.	Grimmia longirostris
51	Basal juxtacostal cells straight, thin-walled; distal juxtacostal lamina 1-stratose, cells often bulging; plants small (less than 1 cm), blackish; moist, alpine habitats.	Grimmia sessitana
51	Basal juxtacostal cells sinuose, thick-walled; distal juxtacostal lamina at least 2-stratose, cells not bulging; plants robust (greater than 1cm), yellow-green to very dark olivaceous; dry, widely distributed	> 52
52	Leaf margins 2-stratose, not thickened; stem central strand present, epidermis thin	> 53
52	Leaf margins multistratose and thickened; stem central strand absent, epidermis thick	> 54
53	Autoicous; costa transverse section reniform; leaves sheathing; widely distributed.	Grimmia longirostris
53	Dioicous; costa transverse section semicircular; leaves not sheathing; American Southwest	Grimmia arizonae
54	Leaves narrowly lanceolate from an ovate base, usually narrowly recurved on both margins; distal lamina without multistratose bands, never papillose.	Grimmia pilifera
54	Leaves broadly lanceolate, broadly recurved on one margin; distal lamina with multistratose bands, occasionally papillose	Grimmia elatior