Plants small, sometimes large, in tufts or loose cushions. Stems erect (creeping in O. kellmanii), branches erect to ascending. Leaves usually erect-appressed and straight when dry, spreading to wide-spreading when moist, ovate, oblong, lanceolate, ligulate, or linear-lanceolate, not rugose; margins entire or denticulate near apex; apex acute, acuminate, apiculate, or obtuse, awn absent (present in O. diaphanum); costa usually ending near apex; basal laminal cells elongate-linear or rectangular; distal cells usually rounded, almost isodiametric, 6–24 µm, papillose only over lumina, papillae 1–4 per cell, conic or 2-fid; marginal cells gradually shorter than basal. Sexual condition gonioautoicous or cladautoicous, rarely dioicous; perichaetial leaves similar to stem leaves or sometimes slightly differentiated. Seta to 6 mm. Capsule immersed, emergent, or exserted, globose to cylindric, smooth or 8- or 16-ribbed, sometimes constricted below mouth when dry; stomata superficial or immersed; peristome double, rarely single or absent; exostome teeth 0, 8, or 16, papillose or striate; endostome segments 0, 8, or 16. Calyptra mitrate, conic-oblong to short-conic, not split at base, smooth or papillose, ± hairy or naked, plicate (not or obscurely plicate in O. gymnostomum and O. obtusifolium), covering entire capsule. Spores isosporous.

Distribution

Nearly worldwide, more common in temperate areas.

Discussion

Species ca. 125 (47 in the flora).

Selected References

Lewinsky, J. 1993. Monographic studies on Orthotrichum (Musci). Bryobrothera 2: 1–59.

Vitt, D. H. 1973. A revision of the genus Orthotrichum in North America, north of Mexico. Bryophyt. Biblioth. 1: 1–108.

Lower Taxa

Orthotrichum affine, Orthotrichum alpestre, Orthotrichum anodon, Orthotrichum anomalum, Orthotrichum bartramii, Orthotrichum bolanderi, Orthotrichum consimile, Orthotrichum cupulatum, Orthotrichum diaphanum, Orthotrichum elegans, Orthotrichum euryphyllum, Orthotrichum exiguum, Orthotrichum fenestratum, Orthotrichum flowersii, Orthotrichum gymnostomum, Orthotrichum hallii, Orthotrichum holzingeri, Orthotrichum keeverae, Orthotrichum kellmanii, Orthotrichum laevigatum, Orthotrichum lescurii, Orthotrichum lyellii, Orthotrichum norrisii, Orthotrichum obtusifolium, Orthotrichum ohioense, Orthotrichum pallens, Orthotrichum parvulum, Orthotrichum pellucidum, Orthotrichum praemorsum, Orthotrichum pulchellum, Orthotrichum pumilum, Orthotrichum pusillum, Orthotrichum pycnophyllum, Orthotrichum pylaisii, Orthotrichum rivulare, Orthotrichum rupestre, Orthotrichum shawii, Orthotrichum shevockii, Orthotrichum sordidum, Orthotrichum speciosum, Orthotrichum spjutii, Orthotrichum stellatum, Orthotrichum stramineum, Orthotrichum strangulatum, Orthotrichum striatum, Orthotrichum tenellum, Orthotrichum underwoodii

Key

1	Leaf apices gradually acute, awns present.	Orthotrichum diaphanum
1	Leaf apices obtuse, acute, acuminate, or cuspidate, awns absent	> 2
2	Leaf margins erect-incurved or involute; leaves ovate, ovate-oblong, or ovate-lanceolate; apices obtuse or rounded; gemmae present; sexual condition dioicous; calyptrae papillose, not or obscurely plicate, naked	> 3
2	Leaf margins plane, reflexed, recurved, revolute, or thick; leaves ± lanceolate, linear, ligulate, or oblong; apices obtuse, acute, acuminate, cuspidate, or mucronate; gemmae absent or present; sexual condition autoicous (dioicous in O. lyellii); calyptrae smooth or rarely papillose, plicate, hairy or naked	> 4
3	Leaf margins involute; distal laminal cell papillae 2 or 3 per cell; peristome absent; Newfoundland.	Orthotrichum gymnostomum
3	Leaf margins erect-incurved; distal laminal cell papillae 1 per cell; peristome present; boreal and western regions.	Orthotrichum obtusifolium
4	Leaves crisped-flexuose when dry; capsules oblong-cylindric or elliptic-cylindric when old, exserted or 1/2 emergent; stomata immersed; Pacific Northwest, Alaska	> 5
4	Leaves erect-appressed, erect, flexuose, or spreading when dry; capsules ovate, oblong, cylindric, or globose, immersed to exserted; stomata superficial or immersed; North America	> 6
5	Plants 8-20 cm; distal laminal cells 7-11 µm; setae (1.5-)2.5-6 mm; capsules exserted to long-exserted, elliptic-cylindric when old; exostome teeth 8, external surface finely papillose, internal surface finely striate; stomata to mid capsule.	Orthotrichum consimile
5	Plants to 1.6 cm; distal laminal cells 8-14 µm; setae (0.8-)1-3(-3.5) mm; capsules barely exserted or sometimes 1/2 emergent, oblong-cylindric; exostome teeth 16, rarely connate in 8 pairs, irregularly papillose-reticulate; stomata in mid and distal capsule.	Orthotrichum pulchellum
6	Leaves 3-4 mm; laminal gemmae present.	Orthotrichum lyellii
6	Leaves usually less than 3 mm; laminal gemmae absent or sometimes present	> 7
7	Stomata superficial; basal laminal cells elongate, walls thick, ± nodose	> 8
7	Stomata immersed; basal laminal cells rectangular, walls thin, not or somewhat nodose	> 26
8	Endostome segments occasionally rudimentary, usually absent; exostome teeth erect, sometimes reflexed when old and dry (recurved in O. shawii); prostome usually present	> 9
8	Endostome segments well developed, usually present when capsule is old; exostome teeth usually recurved or reflexed; prostome absent	> 15
9	Distal laminal cells 2-stratose; leaf margins plane; plants dark green to black.	Orthotrichum bolanderi
9	Distal laminal cells 1-stratose; leaf margins revolute or recurved; plants light green to olive green	> 10
10	Peristome rudimentary, appearing absent.	Orthotrichum spjutii
10	Peristome present, evident	> 11
11	Exostome teeth smooth; distal laminal cells smooth; calyptrae naked; prostome large; on seasonally wet rock.	Orthotrichum holzingeri
11	Exostome teeth papillose; distal laminal cells papillose; calyptrae usually hairy; prostome small or absent; on dry rock	> 12
12	Capsules cylindric or rarely oblong, exserted or rarely sometimes emergent	> 13
12	Capsules globose, ovate, ovate-oblong, short-oblong, or cylindric-ovate, immersed to emergent	> 14
13	Exostome teeth erect; capsules smooth or slightly plicate distally; exothecial cells homogeneous; endostome usually absent in open capsules.	Orthotrichum laevigatum
13	Exostome teeth reflexed-recurved; capsules slightly 8-ribbed distally; exothecial cells differentiated to mid capsule; endostome usually present in at least some capsules.	Orthotrichum pylaisii
14	Exostome teeth erect or sometimes spreading-recurved when old; usually on rock, sometimes trees.	Orthotrichum rupestre
14	Exostome teeth recurved; on trees.	Orthotrichum shawii
15	Exostome teeth reflexed, particularly when old (erect to recurved in O. fenestratum); endostome segments usually 8, narrow, usually of 1 row of cells	> 16
15	Exostome teeth recurved or rarely reflexed; endostome segments 8 or 16, thick, of 2 rows of cells	> 20
16	Capsules usually ovate to ovate-oblong, usually exserted; exostome teeth 16 or 8 splitting to 16	> 17
16	Capsules usually oblong to cylindric, usually emergent to slightly exserted; exostome teeth 8	> 18
17	Exostome fenestrate, cancellate; St. Paul's Island, Alaska.	Orthotrichum fenestratum
17	Exostome not fenestrate or cancellate; Arctic south to California.	Orthotrichum pylaisii
18	Capsules oblong, to 1/2 emergent; exostome teeth perforate only at apices, not cancellate; endostome segments usually absent when capsules are old and dry; leaf apices gradually acuminate- cuspidate; saxicolous; w United States.	Orthotrichum praemorsum
18	Capsules long-cylindric to oblong, 1/2 emergent to exserted, rarely immersed; exostome teeth deeply perforate, cancellate; endostome segments usually present when capsules are old and dry; leaf apices acute; corticolous; n North America. Capsules long-cylindric to cylindric, longer than 1.5 mm, ribbed to 2/3 length, over 1/2 emergent; endostome papillose; w North America.	Orthotrichum affine
19	Capsules oblong to oblong-cylindric, to 1.5 mm, ribbed to 1/2 -2/3 length, usually 1/2-2/3 emergent; endostome smooth or finely verrucose; Great Lakes area, ne North America, Alaska.	Orthotrichum sordidum
20	Calyptrae naked or hairs few near tip; endostome segments hyaline, delicate, as wide as exostome teeth; capsules widest at mouth, ovate-oblong; leaves oblong-lanceolate to oblong; apices rounded-obtuse; plants when mature to 1 cm.	Orthotrichum exiguum
20	Calyptrae hairy; endostome segments yellowish brown, stout, narrower than exostome teeth; capsules widest mid capsule or cylindric; leaves lanceolate, rarely oblong-lanceolate; apices acute to acuminate; plants when mature larger than 1 cm	> 21
21	Sexual condition dioicous; exostome teeth acuminate.	Orthotrichum lyellii
21	Sexual condition autoicous; exostome teeth acute or truncate	> 22
22	Leaf apices slender-acute; exostome teeth truncate, often connate at base; Appalachian Mountains.	Orthotrichum keeverae
22	Leaf apices acute or acuminate; exostome teeth acute, separate to base; absent in Appalachian Mountains	> 23
23	Exostome teeth 16; endostome usually not erose, segments 16; Arizona, New Mexico.	Orthotrichum pycnophyllum
23	Exostome teeth 8, or if 16, endostome erose, segments 8 to 16; temperate and boreal regions southward to California and Missouri	> 24
24	Capsules slightly 8-ribbed to mid capsule.	Orthotrichum speciosum
24	Capsules smooth. Capsules cylindric, emergent to sometimes short-exserted; exostome teeth 8; endostome segments 8.	Orthotrichum elegans
25	Capsules ovate, immersed; exostome teeth 16; endostome segments 16.	Orthotrichum striatum
26	Leaf apices obtuse; margins irregularly dentate at apex, or if entire, apex cucullate; calyptrae naked, papillose; on base of trees near streams or seasonally wet rock, sometimes submerged; west of Continental Divide	> 27
26	Leaf apices acute, narrowly obtuse, apiculate, cuspidate, or mucronate, occasionally obtuse; margins entire or denticulate at apex, occasionally papillose-crenulate; calyptrae naked or hairy, smooth; on trunks of trees or dry rock faces; California or e North America	> 28
27	Plants red-brown to black; leaf apices cucullate; margins entire to sometimes irregularly serrulate near apex; distal laminal cells to 20 µm.	Orthotrichum euryphyllum
27	Plants dark green to blackish; leaf apices flat; margins usually irregularly dentate at apex; distal laminal cells to 13 µm.	Orthotrichum rivulare
28	Capsules smooth, constricted at mouth by 8 short ribs when dry; exostome absent; California.	Orthotrichum anodon
28	Capsules smooth or 8- or 16-ribbed, usually constricted below mouth when dry; exostome present; widespread in North America	> 29
29	Distal laminal cells 2-stratose or rarely with few 1-stratose areas	> 30
29	Distal laminal cells usually 1-stratose, rarely 2-stratose in streaks or with marginal cells 2- to multistratose	> 31
30	Stems erect; leaves similar on vegetative and fertile stems; w North America.	Orthotrichum hallii
30	Primary stems creeping, vegetative and fertile stems erect; leaves differentiated on vegetative and fertile stems; California.	Orthotrichum kellmanii
31	Exostome teeth erect, incurved, or spreading, densely papillose, papillose-striate, striate, or reticulate-papillose; capsules 8- or 16-ribbed	> 32
31	Exostome teeth reflexed or sometimes erect or recurved, finely papillose, rarely striate at apices; capsules smooth or 8-ribbed	> 39
32	Endostome segments 16, filiform, well developed.	Orthotrichum underwoodii
32	Endostome segments absent, or 8, short, not well developed	> 33
33	Capsules exserted, oblong-cylindric to cylindric, usually with 8 long and 8 short ribs; distal laminal cells 1-stratose.	Orthotrichum anomalum
33	Capsules immersed or emergent, rarely short-exserted, ovate or oblong, usually with 8 or 16 ± uniform ribs; distal laminal cells 1- or partially 2-stratose	> 34
34	Capsules 16-ribbed, ovate; leaves ovate-lanceolate to oblong-lanceolate; apices acute or rarely narrowly obtuse; distal laminal cells 1-stratose, rarely 2-stratose in streaks.	Orthotrichum cupulatum
34	Capsules 8- or rarely 16-ribbed, oblong or oblong-ovate, rarely ovate; leaves lanceolate, rarely oblong- or ovate-lanceolate; apices obtuse or blunt, rarely acute; distal laminal cells 1- or 2-stratose	> 35
35	Distal laminal and/or marginal cells 1-7-stratose	> 36
35	Distal laminal cells 1-stratose	> 37
36	Marginal and distal laminal cells mostly to completely 2-stratose.	Orthotrichum hallii
36	Marginal cells 2-7-stratose; distal laminal cells 1-stratose; occasionally with 2-stratose streaks.	Orthotrichum strangulatum
37	Plants appearing glaucous; distal laminal cell papillae large, conic or 2-fid; w North America.	Orthotrichum pellucidum
37	Plants dull; distal laminal cell papillae small, conic; e, c North America	> 38
38	Leaves narrowly lanceolate; margins revolute; capsules ovate; exostome teeth finely papillose.	Orthotrichum lescurii
38	Leaves oblong-lanceolate; margins plane or weakly recurved; capsules oblong; exostome teeth reticulate- papillose.	Orthotrichum parvulum
39	Capsules smooth when dry, wrinkled and slightly 8-plicate when old; exostome teeth 16, erect to recurved; endostome segments usually absent.	Orthotrichum pusillum
39	Capsules 8-ribbed when dry; exostome teeth 8, or 8 splitting to 16, reflexed, occasionally erect or revolute; endostome usually present	> 40
40	Leaf apices cuspidate; margins incurved to form channel at apex; sw United States.	Orthotrichum bartramii
40	Leaf apices obtuse, acute, or apiculate, rarely cuspidate; margins not forming channel at apex; widespread in North America	> 41
41	Stomata to 1/2 covered by subsidiary cells, cells not projecting, inner walls not much thickened; calyptrae usually naked, sometimes hairs few	> 42
41	Stomata 1/2 to completely covered by subsidiary cells, cells projecting, inner walls thickened; calyptrae usually hairy	> 44
42	Leaf apices acute, narrowly obtuse, or apiculate; leaves oblong-lanceolate to broadly lanceolate; distal laminal cells 9-14 µm.	Orthotrichum pallens
42	Leaf apices acute, apiculate, mucronate, or rounded-obtuse; leaves ovate-lanceolate, ovate-oblong, oblong-ligulate, or lanceolate; distal laminal cells 13-20 µm	> 43
43	Leaves ovate-oblong to oblong-ligulate; apices rounded-obtuse, often mucronate, carinate; w North America.	Orthotrichum flowersii
43	Leaves ovate-lanceolate to lanceolate; apices sharply to slenderly acute, usually apiculate, not carinate; North America.	Orthotrichum pumilum
44	Marginal cells 2- or 3-stratose; on dry granite rock.	Orthotrichum shevockii
44	Marginal cells 1-stratose; on trees, mesic rock	> 45
45	Exostome teeth striate-reticulate distally; calyptra hairs strongly papillose; distal laminal cell papillae large, conic or 2-fid; leaves loosely twisted when dry.	Orthotrichum alpestre
45	Exostome teeth papillose; calyptra hairs smooth or papillose by projecting walls; distal laminal cells smooth or papillae low, not 2-fid; leaves stiff, erect-appressed when dry	> 46
46	Vaginula with hairs present	> 47
46	Vaginula with hairs absent	> 48
47	Capsule ribs thin, delicate when dry; California.	Orthotrichum norrisii
47	Capsule ribs thick, broad when dry; Newfoundland.	Orthotrichum stramineum
48	Leaf apices incurved when dry; capsules cylindric to cylindric-elliptic, not constricted below mouth; stomata in proximal 1/3 of capsule, covered by subsidiary cells; restricted to west coast.	Orthotrichum tenellum
48	Leaf apices not incurved when dry; capsules oblong-cylindric or ovate, not to strongly constricted below mouth; stomata mid capsule, covered by subsidiary cells or not; Rocky Mountains and eastward	> 49
49	Distal laminal cells larger than 14 µm, lumina smooth, rounded; leaf apices apiculate or slender-acute, rarely obtuse; leaves ovate-lanceolate to lanceolate; stomata not or to 1/2 covered by subsidiary cells.	Orthotrichum pumilum
49	Distal laminal cells to 13 µm, lumina irregular due to uneven wall thickenings; leaf apices bluntly acute to obtuse; leaves lanceolate to oblong-lanceolate; stomata 1/2 to completely covered by subsidiary cells	> 50
50	Capsules not constricted below mouth, ribs thin, delicate; exostome teeth 8 splitting to 16; subsidiary cells projecting vertically over stomata.	Orthotrichum ohioense
50	Capsules strongly constricted below mouth, ribs thick, broad; exostome teeth 8; subsidiary cells projecting horizontally over stomata.	Orthotrichum stellatum