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BFNA | Family List | BFNA Vol. 2 | Orthotrichaceae

Orthotrichum Hedwig, Spec. Musci. 162. 1801.
[Named for the straight, erect hairs found on the calyptra in many of the species]

Dale H. Vitt

Plants 1--5(--13) cm. Stem leaves imbricate, usually erect-appressed and straight when dry, spreading to wide-spreading when moist, 0.6--6.5 mm; ovate, lanceolate, or linear-lanceolate, obtuse, acute to rounded-acute, acuminate or sometimes obtuse, rarely channeled, rarely acuminate or piliferous; margins reflexed to revolute, rarely plane or involute, entire or denticulate near apex; costa strong, usually ending near apex; distal leaf cells mostly rounded, almost isodiametric, usually 6--24(--30) µm, with 1--3 papillae per cell, papillae conical or forked; basal leaf cells elongate-linear, thick-walled and nodose or rectangular, thin-walled, and smooth near base; marginal leaf cells shorter. Specialized asexual reproduction by brood-bodies, sometimes present on leaves, 3--14 cells long. Perichaetial leaves similar to stem leaves or sometimes slightly differentiated. Sexual condition goniautoicous or cladautoicous, rarely dioicous. Seta to 15 mm, twisted to left. Capsule immersed, emergent or exserted, varying from globose to cylindric, 0.7--3 mm, more or less gradually constricted to seta, smooth or with 8 or 16 ribs and sometimes constricted below mouth when dry; stomates superficial or immersed in central or proximal parts of capsules; peristome double or more rarely single or absent; exostome teeth 0, 8, or 16, papillose or striate, reflexed, recurved, or erect; endostome segments 0, 8, or 16. Calyptra large, mitrate, conic-oblong to short-conic, more or less hairy or naked, plicate or more rarely smooth, not split at base. Spores isomorphic.

Species 120 (40 in the flora); worldwide, more common in temperate areas.


Lewinsky, J. 1993. Monographic studies on Orthotrichum (Musci). Bryobrothera, Vol. 2: 1--59. Vitt, D. H. 1973. A Revision of the Genus Orthotrichum in North America, North of Mexico. Bryophytorum Bibliotheca, 1: 1--108.

1 Leaves ending in ± serrate, hyaline awn.   Orthotrichum diaphanum
+ Leaves obtuse, acute, acuminate, or cuspidate, not ending in hyaline awn.   (2)
2 (1) Leaf margins erect, incurved, or involute; dioicous; leaves ovate or elliptic, with broadly obtuse or rounded apices; calyptrae papillose, not plicate or hairy.   (3)
+ Leaf margins plane, recurved, revolute, or thickened; condition autoicous or if dioicous then leaves acuminate; leaves ± lanceolate or oblong, with narrowly obtuse, acute, or acuminate apices; calyptra smooth or rarely papillose, plicate, hairy, or naked.   (4)
3 (2) Leaf margins involute; distal leaf cells with 2--3 conical papillae per cell; peristome lacking; Newfoundland.   Orthotrichum gymnostomum
+ Leaf margins erect-incurved to incurved; distal leaf cells with 1 papilla per cell; peristome double; common throughout boreal and western regions.   Orthotrichum obtusifolium
4 (2) Leaves crisped-flexuose when dry; capsule cylindric or elliptic-cylindric, fully exserted; stomates immersed; Pacific Northwest and Alaska.   (5)
+ Leaves erect-appressed when dry; capsules various; stomates superficial or immersed; throughout North America.   (6)
5 (4) Plants 0.8--2 mm; distal leaf cells 7--11 µm wide; seta usually 2.5--6 mm; capsule long-exserted, ovate-cylindric when mature; peristome teeth 8, light-brown, finely papillose on the exterior, finely striate on the interior; stomates immersed, in the middle and proximal portion of the capsule.   Orthotrichum consimile
+ Plants usually less than 1.3 cm; distal leaf cells 9--14 µm wide; seta 1.5--3.5 mm; capsule barely exserted, oblong-cylindric when mature; peristome teeth 16, red, irregularly papillose-reticulate; stomates immersed above the middle of the capsule, never in the proximal portion.   Orthotrichum pulchellum
6 (4) Stomates superficial; basal leaf cells elongate, ± nodose, thick-walled.   (7)
+ Stomates immersed; basal leaf cells rectangular, not nodose, thin-walled.   (26)
7 (6) Endostome segments well-developed, usually present when capsule is old; exostome teeth recurved or reflexed; prostome never present; leaves sometimes flexuose when dry, always 1-stratose; usually on trees.   (8)
+ Endostome segments rudimentary or, more often, absent; exostome teeth erect, sometimes reflexed when old and dry; prostome usually present; leaves stiff, erect-appressed when dry, rarely 2-stratose; almost always on rock.   (16)
8 (7) Exostome teeth reflexed; endostome segments 8, narrow, consisting of a single row of cells; capsule strongly 8-ribbed at least 1/2 length of capsule.   (9)
+ Exostome teeth recurved; endostome segments 8 or 16, large, stout, and thick, consisting of 2 rows of cells; capsule smooth or weakly 8-ribbed no more than 1/2 length of capsule or if strongly 8-ribbed, then dioicous.   (10)
9 (8) Exostome fenestrate and cancellate; endemic to St. Paul's Island, Alaska.   Orthotrichum fenestratum
+ Exostome not fenestrate or cancellate, at most perforate at tips; Arctic south to California.   Orthotrichum pylaisii
10 (8) Calyptra oblong-conic, naked; endostome segments hyaline, delicate, as wide as exostome teeth; capsule widest at mouth, ovate; leaves oblong-ovate, rounded-obtuse; plants never longer than 1 cm, largest at apex.   Orthotrichum exiguum
+ Calyptra short-conic, hairy; endostome segments yellowish, stout, not as wide as exostome teeth; capsule widest at middle or cylindric; leaves lanceolate, acute or acuminate; stems longer than 1 cm, of uniform thickness.   (11)
11 (10) Plants dioicous; exostome teeth acuminate; capsule long-cylindric and 8-ribbed.   Orthotrichum lyellii
+ Plants autoicous; exostome teeth acute or truncate; capsule of various types.   (12)
12 (11) Leaves slenderly acute, tip contracted to large, cuspidate point; peristome teeth truncate, often united at base to form basal ring, endemic to Appalachian Mts.   Orthotrichum keeverae
+ Leaves acute or acuminate; peristome teeth acute, separate to base; not found in Appalachian Mts.   (13)
13 (12) Exostome teeth 16, endostome segments 16, usually not erose; New Mexico and Arizona.   Orthotrichum pycnophyllum
+ Exostome teeth 8, or if 16 endostome erose; endostome segments 8 to 16; temperate and boreal regions southward to California and Missouri.   (14)
14 (13) Capsule lightly 8-ribbed.   Orthotrichum speciosum
+ Capsule smooth.   (15)
15 (14) Capsule cylindric, exserted; exostome teeth 8; endostome segments 8.   Orthotrichum elegans
+ Capsule ovate, immersed; exostome teeth 16; endostome segments 16.   Orthotrichum striatum
16 (7) Leaves 2-stratose, margins plane; plants dark-green to black.   Orthotrichum bolanderi
+ Leaves 1-stratose, margins revolute; plants light- to olive-green.   (17)
17 (16) Peristome rudimentary, appearing absent.   Orthotrichum spjutii
+ Peristome present.   (18)
18 (17) Exostome teeth smooth; leaves smooth; calyptra naked; prostome large, extending 1/3 way up exostome; seasonally wet rocks.   Orthotrichum holzingeri
+ Exostome teeth papillose; leaves papillose; calyptra hairy; prostome small or absent; dry rocks.   (19)
19 (18) Capsule cylindric, fully exserted.   (20)
+ Capsule usually oblong and emergent, if cylindric and exserted then strongly 8-ribbed.   (21)
20 (19) Exostome teeth usually 8, reflexed-recurved; capsule lightly 8-ribbed, exothecial cells differentiated for 1/2 length of capsule; endostome usually present in at least some capsules.   Orthotrichum pylaisii
+ Exostome teeth usually 16, erect; capsule smooth or slightly plicate; exothecial cells not or scarcely differentiated; endostome rudimentary, usually absent in open capsules.   Orthotrichum laevigatum
21 (19) Exostome teeth erect; endostome absent.   Orthotrichum rupestre
+ Exostome teeth reflexed; endostome present.   (22)
22 (21) Capsule ovate to ovate-oblong, fully exserted; exostome teeth 16.   (23)
+ Capsule oblong to cylindric, emergent to slightly exserted; exostome teeth 8.   (24)
23 (22) Exostome fenestrate and cancellate; endemic to St. Paul's Island, Alaska.   Orthotrichum fenestratum
+ Exostome not fenestrate or cancellate, at most perforate at tips; Arctic south to California.   Orthotrichum pylaisii
24 (22) Capsule oblong, ± 1/2 emergent; exostome teeth perforate only at tips, not cancellate; endostome segments usually not present when capsules are old and dry; leaves gradually narrowed to a long acuminate-cuspidate apex, which is ± colorless; rare, western states, saxicolous.   Orthotrichum praemorsum
+ Capsule long-cylindric to oblong, 1/2 emergent to exserted; exostome teeth deeply perforate and cancellate, each tooth appearing as split into 4 vertical rows; endostome segments usually present when capsules are old and dry; leaves acute; common, throughout northern North America, corticolous.   (25)
25 (24) Capsule long-cylindric to cylindric, greater than 1.5 mm, ribbed entire length, emergent over 1/2; tapering gradually to seta, which is usually over 1 mm in length; endostome papillose; western North America.   Orthotrichum affine
+ Capsule oblong to oblong-cylindric, less than 1.5 mm, ribbed for ± 1/2 length of capsule, ± emergent; tapering to seta through a long, shriveled neck, which is less than 1.5 mm in length; endostome smooth; Great Lakes area, northeastern North America, and Alaska.   Orthotrichum sordidum
26 (6) Leaves ± obtuse; margins coarsely dentate near apex; calyptra naked, distinctly plicate, papillose, peristome of 8, reflexed teeth; rocks or bases of trees near streams, sometimes submerged; west of continental divide.   Orthotrichum rivulare
+ Leaves ± acute or narrowly obtuse; margins entire or denticulate near apex; calyptra naked or hairy, not distinctly plicate, smooth; peristome various; trunks of trees or dry rock faces; variously distributed.   (27)
27 (26) Exostome teeth erect or spreading, striate, reticulate, or papillose-striate; capsule with 8 or 16 ribs.   (28)
+ Exostome teeth reflexed or recurved, papillose, rarely striate at tips; capsule smooth or 8-ribbed.   (33)
28 (27) Endostome segments 16, linear, papillose, as long as exostome.   Orthotrichum underwoodii
+ Endostome segments absent, or 8 short, not well-developed.   (29)
29 (28) Capsule fully exserted, cylindrical, usually with 8 long and 8 short ribs; leaves 1-stratose.   Orthotrichum anomalum
+ Capsule immersed or emergent, rarely shortly exserted, ovate or oblong, usually with 8 or 16 ± uniform ribs; leaves 1- or 2-stratose.   (30)
30 (29) Capsule with 16 ribs, immersed to 1/3 emergent, ovate and constricted below mouth when dry; leaves ovate-lanceolate, acute, 1-stratose or rarely with 2-stratose streaks.   Orthotrichum cupulatum
+ Capsule with 8 ribs, ± emergent, oblong or oblong-ovate, sometimes constricted below mouth when dry; leaves lanceolate to ligulate, obtuse or blunt, 1- or 2-stratose.   (31)
31 (30) Exostome teeth finely papillose or finely reticulate-papillose, 16, yellowish, erect or spreading-recurved; leaf margins 1--5 cells thick, at least in some leaves thicker than lamina; capsule usually strongly constricted below mouth when old; eastern North America.   Orthotrichum strangulatum
+ Exostome teeth ridged-striate, coarsely striate-reticulate, or coarsely papillose-striate, 8 splitting to 16, white to clear, incurved, spreading, or reflexed; leaf margins not thicker than lamina; capsule only moderately constricted below mouth when dry; western North America.   (32)
32 (31) Leaves 2-stratose or partially 2-stratose, green, lanceolate, obtuse, loosely-appressed, not incurved when dry; papillae small and conical; exostome teeth usually 8.   Orthotrichum hallii
+ Leaves 1-stratose, usually thick and glaucous, ligulate, blunt, stiff, incurved when dry; papillae large, 2-3 forked; exostome teeth ± 16.   Orthotrichum pellucidum
33 (27) Capsule smooth when dry; exostome of 16, erect to recurved teeth; endostome absent.   Orthotrichum pusillum
+ Capsule 8-ribbed when dry; exostome teeth 8, or 8 splitting to 16, reflexed; endostome usually present.   (34)
34 (33) Leaf apex cuspidate and usually denticulate, margins incurved and forming channel at apex; southwestern U.S.A.   Orthotrichum bartramii
+ Leaf apex obtuse, acute, or apiculate, margins not forming channel at apex; throughout North America.   (35)
35 (34) Stomates scarcely to 1/2 covered by non-projecting subsidiary cells, inner walls not much thickened; calyptra usually naked, oblong to conic-oblong.   (36)
+ Stomates 1/2 to completely covered by projecting subsidiary cells, inner walls thickened; calyptra usually with some hairs, oblong.   (38)
36 (35) Leaves acute or narrowly obtuse, never apiculate, oblong-lanceolate to lanceolate; distal leaf cells less than 14 µm; calyptra conic-oblong.   Orthotrichum pallens
+ . Leaves apiculate or rounded-obtuse, ovate or narrowly ovate-lanceolate; distal leaf cells greater than 13 µm; calyptra oblong.   (37)
37 (36) Leaves ovate to ovate-oblong, rounded-obtuse, at least some leaves mucronate, carinate; western North America.   Orthotrichum flowersii
+ Leaves ovate-lanceolate to lanceolate, acute, most leaves apiculate, not carinate; throughout North America.   Orthotrichum pumilum
38 (35) Leaves with 2- to 3-stratose margins; dry granite rocks.   Orthotrichum shevockii
+ Leaves with 1-stratose margins; trees and mesic rocks.   (39)
39 (38) Exostome teeth with striate-reticulate ornamentation in distal portion; calyptra with strongly papillose hairs; leaf cells papillose, with regular, long-forked papillae; leaves slightly twisted when dry; capsule strangulate when dry.   Orthotrichum alpestre
+ Exostome teeth papillose; calyptra hairs smooth or papillae formed by projecting cell walls; leaf cells smooth or with low, conical papillae, papillae never forked; leaves stiff, erect-appressed when dry; capsule variously constricted beneath mouth when dry.   (40)
40 (39) Vaginula with numerous hairs.   Orthotrichum stramineum
+ Vaginula without hairs.   (41)
41 (40) Leaf tips incurved when dry; capsule cylindric to cylindric-elliptic, not constricted beneath mouth, but contracted along entire length; stomates in proximal 1/3 of capsule, completely covered by subsidiary cells; restricted to west coast.   Orthotrichum tenellum
+ Leaf tips not incurved when dry; capsule oblong-cylindric, constricted beneath mouth, never contracted along entire length; stomates at middle of capsule; Rocky Mountains and eastward.   (42)
42 (41) Leaf cells greater than 14 µm, the lumina smooth and rounded; leaves apiculate or slenderly acute, ovate-lanceolate to oblong-lanceolate; subsidiary cells not completely covering stomates.   Orthotrichum pumilum
+ Leaf cells less than 14 µm, lumina irregular due to uneven wall thickenings; leaves broadly acute to obtuse, lanceolate; subsidiary cells completely covering stomates.   (43)
43 (42) Capsule strongly constricted beneath mouth, brown; exothecial cells with thickened walls, in rows 6--8 cells wide; exostome teeth 8; subsidiary cells projecting horizontally over stomate.   Orthotrichum stellatum
+ Capsule not constricted beneath mouth, yellow; exothecial cells with thickened walls in rows 4--6 cells wide; peristome teeth 16, rarely united into 8 pairs; subsidiary cells projecting upward over stomate.   Orthotrichum ohioense

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