Bryophyte Flora of North America

Key to the Moss Genera of North America North of Mexico

Dale H. Vitt and William R. Buck

Based on a key originally published in Contributions from the University of Michigan Herbarium 18: 43-71. 1992, which holds the copyright.

1. Gametophytes seemingly absent (consisting only of protonemata); sporophytes of asymmetric capsules and papillose setae.	Buxbaumia
1. Gametophytes present (with obvious leaves); sporophytes various.	2
2. Leaf cells arranged in a network of narrow, green cells alternating with large hyaline cells; branches usually in clusters.	Sphagnum
2. Leaf cells of one kind (green), or if of two kinds, branches never in clusters.	3
3. Leaves attached in two rows on opposite sides of the stem (distichous).	4
3. Leaves attached all around the stem (foliate stems sometimes flattened [complanate]).	7
4. Leaves appearing split at the base, consisting of two vaginant laminae which clasp the stem and base of the leaf above (equitant).	Fissidens
4. Leaves with expanded bases, not clasping leaf above.	5
5. Leaves ecostate; protonemata luminous.	Schistostega
5. Leaves unicostate; protonemata not luminous.	6
6. All leaves with a rough (papillose), linear subula.	Distichium
6. Vegetative leaves with a smooth mucro; perichaetial leaves with a smooth subula.	Bryoxiphium
7. Leaves with lamellae or filaments on the adaxial (upper) surface of the costa (excluding  propagula).	8
7. Leaves without lamellae or filaments on the adaxial surface of the costa (but propagula sometimes present).	23
8. Leaves with filaments on the adaxial surface of the costa.	9
8. Leaves with lamellae on the adaxial surface of the costa.	10
9. Leaf margins broadly inrolled (and mostly obscuring the filaments).	Aloina
9. Leaf margins reflexed to revolute	Crossidium
10. Leaves bordered with elongate cells.	Atrichum
10. Leaves without elongate, marginal cells.	11
11. Leaves ciliate at upper part of hyaline sheath.	Bartramiopsis
11. Leaves eciliate.	12
12. Upper leaf margins bistratose with paired, multicellular teeth; leaf apices with slender, smooth, caducous awns; restricted to the arctic.	Lyellia
12. Upper leaf margins unistratose with single teeth or entire; leaf apices muticous or with serrate awns.	13
13. Lamellae 2-4; leaves hyaline awned; plants small, less than 5 mm; peristome none or rudimentary and fragile.	Pterygoneurum
13. Lamellae 4-50; leaves mostly not awned; plants mostly larger; peristome of 32 or 64 persistent teeth.	14
14. Lamellae distinctly wavy.	15
14. Lamellae straight.	16
15. Upper leaf margins with border of hyaline, short- rhombic cells.	Psilopilum
15. Upper leaf margins not bordered.	Oligotrichum
16. Leaf laminae with teeth on abaxial (back) surface; calyptrae naked or with a few hairs.	Oligotrichum
16. Leaf laminae smooth at back; calyptrae densely hairy.	17
17. Plants with capsules.	18
17. Plants without capsules.	20
18. Capsules (2-)4(-6)-angled.	Polytrichum
18. Capsules cylindric.	19
19. Capsules without stomates; lumina of apical cells of lamellae not pyriform.	Pogonatum
19. Capsules with stomates; lumina of apical cells of lamellae pyriform.	Polytrichastrum
20. Apical cells of lamellae smooth or with faint cuticular ridges.	21
20. Apical cells of lamellae papillose.	22
21. Plants small, less than 6 mm high; leaves never awned.	Pogonatum
21. Plants larger; leaves with or without awns.	Polytrichum
22. Apical cells of lamellae rounded, quadrate or oblate.	Pogonatum
22. Apical cells elliptic-pyriform.	Polytrichastrum
23. Leaves deeply lobed with lobes linear-terete.	Takakia
23. Leaves never lobed, flattened (although sometimes concave with margins inrolled or recurved).	24
24. Leaves without a costa or costa short and double, double, or single with 2-3 lateral spurs.	25
24. Leaves with a single costa to at least midleaf.	114
25. Although appearing none, costa single and occupying entire leaf area, thus leaf appearing multistratose.	26
25. Costa truly none or double; lamina always unistratose.	27
26. Leaves ligulate; green cells (chlorocysts) three- sided in section.	Octoblepharum
26. Leaves lanceolate; green cells four-sided in section.	Leucobryum
27. Upper leaf cells papillose or prorulose.	28
27. Upper leaf cells smooth (rarely with minute cuticular roughenings).	46
28. Leaf apices hyaline.	29
28. Leaf apices concolorous.	30
29. Leaf cells with a single, unbranched papillae (on each surface); capsules exserted, ribbed; perichaetial leaves entire; restricted to western North America.	Pseudobraunia
29. Leaf cells with 1-2 forked papilla (on each surface); capsules immersed, smooth; perichaetial leaves ciliate; widespread.	Hedwigia
30. Leaf cells pluripapillose.	31
30. Leaf cells unipapillose or prorulose.	33
31. Papillae arranged in rows over the lumina; leaf cells more than 5:1.	Taxithelium
31. Papillae randomly arranged over lumina; leaf cells less than 4:1.	32
32. Leaves obtuse; stems complanate-foliate.	Erpodium
32. Leaves short-acuminate; stems symmetrically foliate.	Braunia
33. Plants 2-3 pinnate, each year forming a flattened frond, the fronds arranged in a stair-step ascending pattern.	Hylocomium
33. Plants simple or 1-pinnate, not forming ascending fronds.	34
34. Leaves plicate.	35
34. Leaves not plicate.	36
35. Costa double and extending to above midleaf; leaves spreading to squarrose.	Rhytidiadelphus
35. Costa short and double; leaves falcate-secund.	Ctenidium
36. Plants reddish-black, occurring tightly attached to rocks.	Andreaea
36. Plants greenish, occurring on various substrates.	37
37. Plants minute, less than 2 mm, acrocarpous.	Ephemerum
37. Plants large, more than 1 cm, pleurocarpous.	38
38. Costa strong and double, extending to near leaf apex.	Callicostella
38. Costa short and double, ending below midleaf.	39
39. Alar cells numerous, oblate to rounded, strongly differentiated and extending up the margins; restricted to Pacific Northwest.	Pterogonium
39. Alar cells few, mostly quadrate, scarcely extending up the margins; widespread.	40
40. Cells at midleaf more than 5:1.	41
40. Cells at midleaf less than 5:1.	43
41. Apical leaf cells much shorter than those at midleaf.	Taxiphyllum
41. Apical leaf cells scarcely differentiated.	42
42. Leaves slenderly acuminate; prorulose at both upper and lower ends of cells.	Chrysohypnum
42. Leaves acute; prorulose only at upper ends of cells.	Leptohymenium
43. Stem and branch leaves differentiated.	Heterocladium
43. Stem and branch leaves similar.	44
44. Leaves broadly ovate, concave, obtuse to obtuse- apiculate.	Myurella
44. Leaves lanceolate to ovate-lanceolate, acute to acuminate.	45
45. Leaves acute, serrulate only above; propagula often in leaf axils; northern in distribution.	Pterigynandrum
45. Leaves acuminate, serrulate throughout; propagula absent; eastern U.S. in distribution.	Schwetschkeopsis
46. Leaves ending in a hyaline awn.	47
46. Leaves concolorous at apex.	48
47. Leaf cells 2:1 or less, oblate-hexagonal throughout; eperistomate.	Erpodium
47. Leaf cells more than 3:1, upper cells short rhomboidal, basal cells quadrate; peristomate.	Venturiella
48. Plants aquatic, occurring submerged at least part of the year; leaves keeled or flat.	Fontinalis
48. Plants sometimes in wet habitats but never occurring submerged; leaves various but never keeled.	49
49. Plants acrocarpous, usually less than 4 cm.	50
49. Plants pleurocarpous, mostly larger.	53
50. Plants occurring on rock.	51
50. Plants occurring on bare soil.	52
51. Plants reddish-black; capsules valvate.	Andreaea
51. Plants greenish-brown; capsules with four peristome teeth.	Tetrodontium
52. Protonemata abundant; capsules ovoid, apiculate; calyptrae campanulate-mitrate, deciduous.	Ephemerum
52. Protonemata sparse; capsules globose; calyptrae very small, persistent.	Micromitrium
53. Costa single with one or sometimes two supplementary costae on each side.	Antitrichia
53. Costa always double, or if single very short and without supplementary costae.	54
54. Costa long and double, extending to or beyond midleaf.	55
54. Costa short and double, usually ending just above leaf base.	59
55. Stems with numerous paraphyllia.	56
55. Stems lacking paraphyllia.	57
56. Stem leaves plicate, decurrent.	Hylocomiastrum
56. Stem leaves not plicate or decurrent.	Loeskeobryum
57. Leaf cells thin-walled, lax, abruptly bordered by elongate cells.	Cyclodictyon
57. Leaf cells firm-walled, not or only gradually bordered.	58
58. Plants forming mats; leaves falcate-secund at least at branch apices; exostome teeth striate, furrowed.	Trachyxiphium
58. Plants tufted; leaves somewhat contorted when dry but not falcate; exostome teeth papillose, not furrowed.	Lepidopilum
59. Leaves obtuse; plants small, rare, restricted to the mountains of southeastern U.S..	60
59. Leaves acute to acuminate, at least apiculate; plants mostly larger, widespread.	61
60. Leaves asymmetric with a basal lobe.	Homaliadelphus
60. Leaves symmetric without lobe.	Bryocrumia
61. Leaf cells lax, hexagonal.	62
61. Leaf cells firm- to thick-walled, rounded to linear.	63
62. Lateral and dorsal leaves differentiated in areolation; stems pinnately branched.	Vesicularia
62. Lateral and dorsal leaves with similar areolation; stems irregularly branched.	Hookeria
63. Leaves slenderly long-decurrent.	Plagiothecium
63. Leaves not at all decurrent to broadly auriculate.	64
64. Plants slender, thread-like; leaves mostly less than 1 mm long.	65
64. Plants larger; leaves more than 1 mm long.	67
65. Branch leaves more than 0.5 mm long.	Homomallium
65. Branch leaves less than 0.5 mm long.	66
66. Costa short and single; leaf cells rounded-elliptic.	Pseudoleskeella
66. Costa none or very short and double; leaf cells rhombic.	Platydictya
67. Leaves falcate-secund.	68
67. Leaves straight.	84
68. Upper leaf cells oblong-rhombic, ca. 3:1.	69
68. Leaf cells more or less linear, more than 6:1.	70
69. Alar cells numerous, oblate, extending up the margins in many rows.	Leucodon
69. Alar cells few, oblong-quadrate, in 1-2 rows along the insertion.	Sematophyllum
70. Plants regularly and closely pinnate, feather-like; fronds flat, erect to ascending, oblong-triangular.	Ptilium
70. Plants irregularly pinnate to unbranched, not feather-like; stems prostrate to loosely ascending.	71
71. Mature branches erect and producing abundant and conspicuous propagula in their upper leaf axils.	Platygyrium
71. Branches not producing propagula in leaf axils.	72
72. Branches curved-secund when dry, erect when moist; alar cells small and quadrate.	Pylaisiella
72. Branches little altered when dry; alar cells various.	73
73. Alar cells when differentiated quadrate, sometimes enlarged but not at all inflated.	74
73. Alar cells quadrate to oblong, inflated.	79
74. Stems with paraphyllia.	Rhytidiopsis
74. Stems without paraphyllia.	75
75. Plants very large (stem leaves 3.5-5.0 mm), stems ascending to erect; leaves plicate.	Rhytidiadelphus
75. Plants smaller (stem leaves less than 3.5 mm), stems prostrate to ascending; leaves various.	76
76. Alar cells none or very few; pale propagula often clustered in leaf axils.	Isopterygiopsis
76. Alar cells distinctly differentiated.	77
77. Plants occurring on wet rocks in mountain streams.	Hygrohypnum
77. Plants in various habitats but not as above.	78
78. Costa to ca. 1/3 the leaf length with the two forks not meeting at the base; plants of Alaska and Yukon.	Gollania
78. Costa mostly shorter, the forks joining at the base; plants widespread.	Hypnum
79. Plants occurring in calcareous fens or marl pools, dark reddish-brown; leaves obtuse.	Scorpidium
79. Plants occurring in other habitats, golden to green; leaves acute to acuminate.	80
80. Plants occurring on wet rocks in mountain streams.	Hygrohypnum
80. Plants in various habitats but not as above.	81
81. Alar cells thick-walled, inflated in several rows; leaf margins strongly serrate.	Heterophyllium
81. Alar cells inflated in 1(-2) rows, or if more, thin- walled; leaf margins entire to serrulate.	82
82. Stems surrounded by enlarged, thin-walled, hyaline cortical cells (hyalodermis); alar cells in large, subdecurrent areas.	Hypnum
82. Stems surrounded by small, thick-walled, concolorous cells; alar cells in 1(-2) rows.	83
83. Plants very shiny; leaves 0.8-1.4 mm long, densely serrulate above; capsules inclined, asymmetric.	Brotherella
83. Plants slightly shiny; leaves 0.5-1.1 mm long, distantly serrulate above; capsule erect, symmetric.	Pylaisiadelpha
84. Stem leaves abruptly contracted to long setaceous point.	85
84. Stem leaves acute, acuminate or apiculate.	86
85. Leaf apices hyaline; alar cells scarcely differentiated.	Iwatsukiella
85. Leaf apices yellow; alar cells inflated and hyaline.	Wijkia
86. Leaves squarrose-recurved when dry, with channeled apices.	87
86. Leaves erect to spreading, or if squarrose only when moist, the apices mostly not channeled.	88
87. Stem leaves greater than 2.5 mm long; alar cells oblong, somewhat inflated, intramarginal.	Rhytidiadelphus
87. Stem leaves less than 2.5 mm long; alar cells subquadrate, not at all inflated, marginal.	Campylium
88. Plants occurring on wet rocks in mountain streams; leaves ovate, concave.	Hygrohypnum
88. Plants in other habitats but not as above; leaves various.	89
89. Stems complanate-foliate.	90
89. Stems symmetrically foliate.	96
90. Alar cells numerous and quadrate; capsules erect.	Entodon
90. Alar cells few, variously shaped; capsules usually inclined.	91
91. Plants occurring on vertical substrates, tree trunks or rocks.	Neckera
91. Plants occurring on horizontal substrates, rarely the extreme bases of trees.	92
92. Leaf margins serrulate throughout.	93
92. Leaf margins entire or serrulate only in upper half.	94
93. Apical leaf cells shorter than those at midleaf.	Taxiphyllum
93. Apical leaf cells undifferentiated.	Herzogiella
94. Rhizoids arising from leaf axils, papillose; leaf margins more or less entire.	Isopterygiopsis
94. Rhizoids arising from below leaf insertion, smooth; leaf margins serrulate above.	95
95. Pseudoparaphyllia filamentous; annuli not differentiated; plants mostly monoicous.	Isopterygium
95. Pseudoparaphyllia absent; annuli differentiated; plants mostly dioicous.	Pseudotaxiphyllum
96. Alar cells inflated.	97
96. Alar cells rectangular to quadrate, not inflated.	101
97. Plants erect; stems with hyalodermis; alar cells hyaline and in auricles.	Calliergonella
97. Plants prostrate; stems without hyalodermis; alar cells yellowish, not in auricles.	98
98. Alar cells uniform, without an enlarged basal row; stem apices flattened.	Callicladium
98. Alar cells with an enlarged basal row; stem apices not flattened.	99
99. Alar cells rounded to the insertion; exostome teeth furrowed.	Acroporium
99. Alar cells not rounded to insertion; exostome teeth not furrowed.	100
100. Exostome teeth striate; endostome with evident basal membrane and segments; eastern North America.	Sematophyllum
100. Exostome teeth smooth or faintly papillose; endostome fugaceous, appearing absent; restricted to central Florida in oak scrub.	Donnellia
101. Plants with numerous (more than 50), quadrate alar cells, extending up the margins by more than 12 rows.	102
101. Plants with fewer (less than 25), quadrate to rectangular alar cells, extending up the margins in less than 8 rows.	107
102. Stems with numerous paraphyllia.	Alsia
102. Stems lacking paraphyllia.	103
103. Leaves less than 0.8 mm long; cells with obscure cuticular roughenings; western montane.	Leptopterigynandrum
103. Leaves more than 1 mm long; cells smooth.	104
104. Alar cells extending up the margins for less than 1/6 the leaf length.	105
104. Alar cells extending up the margins for more than 1/3 the leaf length.	106
105. Leaves acuminate, somewhat decurrent; endostome with cilia; plants restricted to coastal western North America, California to British Columbia.	Tripterocladium
105. Leaves mostly obtuse to acute, rarely acuminate, never decurrent; endostome lacking cilia; plants widespread but not in coastal western North America.	Entodon
106. Secondary stems freely subpinnately branched.	Forsstroemia
106. Secondary stems simple or with few branches.	Leucodon
107. Plants epiphytic with creeping primary stems and erect secondary stems.	108
107. Plants terrestrial or rarely on bases of trees, primary and secondary stems not differentiated.	109
108. Secondary stems unbranched; leaves spreading with squarrose tips; propagula common.	Jaegerina
108. Secondary stems irregularly branched; leaves erect; propagula absent.	Neomacounia
109. Stems with hyalodermis; leaf margins serrulate to base.	Herzogiella
109. Stems without hyalodermis; leaf margins entire or serrulate above.	110
110. Leaves plicate.	Orthothecium
110. Leaves not plicate.	111
111. Leaf apices obtuse-apiculate.	112
111. Leaf apices acuminate.	113
112. Plants occurring in fens; stems green, sparsely branched.	Pseudocalliergon
112. Plants widespread in acidic habitats of the boreal forest; stems reddish-orange, pinnately branched.	Pleurozium
113. Leaf cells porose throughout; pseudoparaphyllia absent or foliose; plants in boreal, arctic and alpine habitats.	Orthothecium
113. Leaf cells not porose except at insertion; pseudoparaphyllia filamentous; plants of coastal eastern North America inland to the Midwest.	Isopterygium
114. Plants erect, dendroid or frondose from a nonbranched stipe.	115
114. Plants prostrate to erect, simple to pinnately branched.	121
115. Leaves bordered by elongate cells.	116
115. Leaves not bordered.	117
116. Plants with two kinds of leaves, the larger ones with costa ending well below apex, the smaller ones (amphigastria) with excurrent costa.	Hypopterygium
116. Plants with leaves all of one kind, the costa subpercurrent.	Leucolepis
117. Stems with paraphyllia or filamentous, paraphyllia-like structures.	118
117. Stems without paraphyllia.	120
118. Plants epiphytic; stems pinnately frondose, curled when dry, spreading when moist.	Dendroalsia
118. Plants terrestrial (rarely on tree bases); stems dendroid, little altered when dry.	119
119. Branch leaves long-decurrent, the decurrencies of inflated, hyaline cells; stems with lamellae; stem leaves with entire margins.	Pleuroziopsis
119. Branch leaves cordate to auriculate, the auricles not inflated; stems with paraphyllia; stem leaves with serrate margins.	Climacium
120. Apical cells of branch leaves rhombic; costa of branch leaves strong, not tapering toward apex.	Thamnobryum
120. Apical cells of branch leaves long-hexagonal; costa of branch leaves slender, tapering toward apex.	Porotrichum
121. Plants blackish, tightly attached to rocks in arctic and montane areas; capsules valvate.	122
121. Plants greenish to blackish, on various substrates; capsules cleistocarpous or operculate, never valvate.	123
122. Plants occurring on calcareous rocks; capsules not hygroscopic, turbinate, obtuse-conic.	Andreaeobryum
122. Plants occurring on acidic rocks; capsules hygroscopic, when moist elliptic, tapering to a point.	Andreaea
123. Leaves strongly squarrose-recurved wet or dry; plants occurring in fens.	Paludella
123. Leaves erect to squarrose; plants occurring in various habitats.	124
124. Stems with paraphyllia.	125
124. Stems lacking paraphyllia.	142
125. Stems complanate-foliate; stem leaves undulate.	Metaneckera
125. Stems symmetrically foliate; leaves not undulate.	126
126. Alar cells inflated in well marked groups.	127
126. Alar cells mostly not differentiated, if so, not inflated.	128
127. Stem leaves deeply plicate; paraphyllia filamentous, abundant.	Palustriella
127. Stem leaves not plicate; paraphyllia foliose, sparse to abundant.	Cratoneuron
128. Paraphyllia with short cells, 1-3:1.	129
128. Paraphyllia with elongate cells, more than 5:1.	140
129. Cells of paraphyllia papillose.	130
129. Cells of paraphyllia smooth.	134
130. Leaf cells unipapillose.	131
130. Leaf cells pluripapillose.	132
131. Plants once-pinnate; leaf cells papillose on both surfaces.	Abietinella
131. Plants 2-3-pinnate; leaf cells papillose only at back.	Thuidium
132. Plants large, dioicous; leaf cells papillose only at back.	Thuidium
132. Plants small, autoicous; leaf cells papillose on both surfaces.	133
133. Plants once-pinnate; leaves not incurved when dry; leaf cells strongly bulging; setae smooth.	Rauiella
133. Plants 1-2-pinnate; leaves incurved when dry; leaf cells flat; setae smooth or papillose.	Cyrto-hypnum
134. Papillae of leaf cells large, either forked or elongate and curved; leaves broadly ovate.	Thelia
134. Papillae of leaf cells short, simple; leaves lanceolate to ovate-lanceolate.	135
135. Costa pellucid; leaves usually with hair-points.	Claopodium
135. Costa opaque; leaves lacking hair-points.	136
136. Stem and branch leaves differentiated.	Haplocladium
136. Stem and branch leaves uniform.	137
137. Leaf cells isodiametric or nearly so, hexagonal to short-rhombic.	138
137. Leaf cells elongate, oblong-rhombic to oblong-linear.	139
138. Capsules inclined, asymmetric; exostome teeth striate; plants largely western.	Pseudoleskea
138. Capsules erect, symmetric; exostome teeth pale and papillose; plants largely eastern.	Leskea
139. Capsules erect, symmetric; endostome segments narrow, not keeled.	Lescuraea
139. Capsules inclined, asymmetric; endostome segments broader, keeled.	Pseudoleskea
140. Leaf margins entire to serrulate.	Helodium
140. Leaf margins strongly serrate in upper half.	141
141. Upper leaf cells short, 2-5:1; plants of southeastern United States.	Climacium
141. Upper leaf cells linear, more than 8:1; plants widespread.	Hylocomiastrum
142. Plants whitish; leaves composed mostly of costa, multistratose, with small green cells enclosed between 2 layers of hyaline cells on both surfaces.	143
142. Plants greenish to blackish, rarely whitish; leaves usually with conspicuous lamina, if not green cells and hyaline cells of about equal size with only a single layer of hyaline cells on either side of the green cells.	144
143. Green cells in section 4-sided; plants terrestrial.	Leucobryum
143. Green cells in section 3-sided; plants epiphytic.	Octoblepharum
144. Leaf margins strongly incurved to involute, at least when dry.	145
144. Leaf margins plane to recurved.	149
145. Leaf margins incurved wet or dry.	146
145. Leaf margins incurved when dry, plane when moist.	148
146. Leaf cells papillose; costa with two stereid bands.	147
146. Leaf cells smooth; costa with one stereid band.	Indusiella
147. Capsules exserted, operculate.	Weissia
147. Capsules immersed to emergent, cleistocarpous.	Astomum
148. Costa with single stereid band; peristome present.	Plaubelia
148. Costa with two stereid bands; peristome absent.	Hyophila
149. Plants minute, occurring on soil (or rarely rock), ephemeral, often with persistent protonemata; capsules immersed.	150
149. Plants mostly larger, occurring on various substrates, mostly not ephemeral, or if so, capsules exserted.	161
150. Capsules operculate.	151
150. Capsules cleistocarpous.	152
151. Exothecial cells collenchymatous.	Aphanorrhegma
151. Exothecial cells not thickened at corners.	Physcomitrium
152. Spores few per capsule, more than 100 µm in diameter.	153
152. Spores numerous per capsule, less than 60 µm in diameter.	154
153. Leaves broadly ovate or elliptic, abruptly narrowed to an awn; plants with slender, subterranean rhizomes.	Lorentziella
153. Leaves oblong to lanceolate, acute to subulate; plants not rhizomatous.	Archidium
154. Leaves ovate to broadly ovate, abruptly cuspidate to apiculate.	155
154. Leaves narrowly lanceolate to oblong; costa subpercurrent to subulate.	157
155. Leaf cells pluripapillose with C-shaped papillae; leaf margins revolute.	Phascum
155. Leaf cells smooth or with 1-2 blunt, conical papillae; leaf margins plane to erect	156
156. Plants bulbiform, occurring on soil; leaves very broad and deeply concave with a reflexed tip..	Acaulon
156. Plants not bulbiform, occurring on the underside of quartz pebbles; leaves oblong-lanceolate to oblong-ovate, the tip not reflexed.	Aschisma
157. Capsules pyriform with a conspicuous stomatose neck.	Bruchia
157. Capsules globose to broadly elliptic without a conspicuously differentiated neck.	158
158. Costa long excurrent, at least on perichaetial leaves.	Pleuridium
158. Costa subpercurrent.	159
159. Leaf margins spinose-serrulate throughout.	Ephemerum
159. Leaf margins entire or serrulate above.	160
160. Leaves lanceolate.	Pseudephemerum
160. Leaves oblong-lanceolate to obovate.	Physcomitrella
161. Neck of capsules (apophysis) as wide or wider than upper portion (urn); occurring on dung and animal remains.	162
161. Neck of capsules considerably narrower than urn; occurring on various substrates.	164
162. Capsules dumb-bell shaped when mature; seta hyaline; restricted to the arctic.	Aplodon
162. Capsules (at least the urn) cylindric; seta colored; widespread.	163
163. Apophyses narrowly pyriform, the same color or darker than the urn; peristome teeth joined in 4's, later in 2's, not chambered.	Tetraplodon
163. Apophyses globose to turbinate, sometimes becoming umbrella-like, differentiated in color; peristome teeth sometimes approximate or fused in pairs, chambered.	Splachnum
164. Leaves of two kinds, large lateral ones and smaller dorsal ones.	165
164. Leaves all of one kind.	166
165. Leaves bordered; plants erect, occurring along the Pacific coast.	Epipterygium
165. Leaves unbordered; plants prostrate, restricted to southern Florida.	Racopilum
166. Capsules cleistocarpous; plants rare.	167
166. Capsules operculate; plants rare to common.	169
167. Plants known only from New Hampshire; occurring on wet soil.	Bruchia
167. Plants known from arctic and alpine tundra on animal-derived substrates.	168
168. Capsules broadest in lower half.	Voitia
168. Capsules broadest in upper half.	Tetraplodon
169. Cells with nodulose-wavy walls throughout the leaf, sometimes most conspicuous toward leaf base when upper cells short.	Racomitrium
169. Cells without nodulose-wavy walls, or if present only near insertion.	170
170. Leaves with hyaline hair-points.	171
170. Leaves without hair-points, or if with hairpoints not hyaline.	181
171. Costa broad, filling 1/4 or more of the leaf base.	Campylopus
171. Costa narrower.	172
172. Upper leaf cells densely pluripapillose with C-shaped papillae.	173
172. Upper leaf cells smooth or with low, indistinct papillae.	174
173. End walls of basal cells thickened; calyptrae large, mitrate and covering capsule.	Encalypta
173. End walls of basal cells not thickened; calyptrae small, cucullate.	Tortula
174. Cells smooth, lax, thin-walled, hexagonal to rhombic.	175
174. Cells obscurely papillose, firm-walled, rounded to quadrate.	177
175. Leaves not bordered.	Stegonia
175. Leaves bordered.	176
176. Plants usually epiphytic; capsules erect.	Brachymenium
176. Plants terrestrial or saxicolous; capsules inclined.	Bryum
177. Plants occurring on trees.	Orthotrichum
177. Plants occurring on rocks and soil.	178
178. Perichaetial leaves differentiated in size and shape; capsules immersed.	Schistidium
178. Perichaetial leaves similar to upper vegetative leaves; capsule immersed or exserted.	179
179. Calyptrae scarcely longer than the operculum, cucullate or mitrate, smooth.	Grimmia
179. Calyptrae large, covering the capsule to the middle or below, campanulate-mitrate, striate or plicate.	180
180. Leaves lanceolate; annuli none; calyptrae plicate.	Coscinodon
180. Leaves ovate to obovate; annuli well developed; calptrae striate.	Jaffueliobryum
181. Costa very broad, occupying 1/3-1/2 the leaf base and filling the subula (plants entirely acrocarpous).	182
181. Costa narrower, or if broad then ending below the leaf apex and not filling it (or if broad then pleurocarpous).	187
182. Alar cells well diffentiated.	183
182. Alar cells poorly differentiated.	185
183. Costa without guide cells or stereids, in transverse section with a median layer of green cells enclosed dorsally and ventrally with hyaline cells.	Paraleucobryum
183. Costa nearly always with guide cells and stereids, without enclosed green cells.	184
184. Inner basal cells of leaf pale, enlarged, and broadly rectangular, extending upward along the costa; capsules smooth; annuli none; calyptrae not fringed.	Dicranodontium
184. Inner basal cells not conspicuously differentiated along the costa; capsules furrowed; annuli compound; calyptrae usually fringed.	Campylopus
185. Capsules with a neck at least as long as the urn; costa filling no more than 1/3 of the leaf base.	Trematodon
185. Capsules with a short, inconspicuous neck; costa filling 1/2 or more of the leaf base.	186
186. Leaves 3.5-5.0 mm long; upper laminal cells elongate, 75-140 µm long; brood leaves absent.	Campylopodiella
186. Leaves 2.0-3.0 mm long; upper laminal cells rectangular, 25-55 µm long; brood leaves usually present, often abundant.	Brothera
187. Plants pleurocarpous (sporophytes lateral); stems mostly prostrate with lateral branches, often mat- forming, or stems prostrate with erect branches bearing terminal sporophytes (cladocarpous).	188
187. Plants acrocarpous (sporophytes terminal); stems erect, not branched or occasionally branched beneath inflorescences.	280
188. Leaves bordered by elongate cells, sharply differentiated from shorter inner cells.	189
188. Leaves not bordered by elongate cells.	191
189. Plants epiphytic; border unistratose.	Daltonia
189. Plants aquatic; border 2-5-stratose.	190
190. Margins serrate almost to base; leaves ovate-oblong to ovate-lanceolate, acuminate; plants of Oregon.	Limbella
190. Margins serrulate; leaves ovate, often broadly so, bluntly acute; plants of eastern North America.	Platylomella
191. Leaf cells papillose or prorulose.	192
191. Leaf cells smooth.	205
192. Leaves rugose and plicate.	Rhytidium
192. Leaves not rugose, rarely plicate.	193
193. Leaf cells pluripapillose.	194
193. Leaf cells unipapillose or prorulose.	198
194. Papillae arranged in a row over the cell lumina; cells longer than 3:1.	195
194. Papillae randomly arranged over the cells; cells more or less isodiametric.	196
195. Plants stiff, dark green to blackish; leaves ovate, plicate, cordate.	Papillaria
195. Plants soft, bright green (when alive); leaves lanceolate, smooth, not cordate.	Barbella
196. Leaf apices fragile.	Haplohymenium
196. Leaf apices not fragile.	197
197. Leaves strongly inrolled when dry; marginal basal cells elongate, smooth; sporophytes terminal on branches.	Macromitrium
197. Leaves loosely erect to contorted; marginal basal cells rounded, papillose; sporophytes lateral.	Anomodon
198. Cells unipapillose over the lumina.	199
198. Cells prorulose.	201
199. Upper leaf cells linear-flexuose; uniseriate propagula common in leaf axils.	Henicodium
199. Upper leaf cells short, 1-3:1; asexual reproduction absent or by branchlets.	200
200. Leaves ovate-lanceolate, narrowed to a nonpapillose, pale acumen, squarrose when moist.	Lindbergia
200. Leaves oblong-ovate, bluntly acute, loosely erect and more or less complanate.	Stereophyllum
201. Leaf cells short, 1-3:1.	202
201. Leaf cells more than 5:1.	203
202. Leaves appressed when dry, wide-spreading when moist; perichaetial leaves strongly differentiated; capsules immersed.	Cryphaea
202. Leaves little altered when moist; perichaetial leaves scarcely differentiated; capsules exserted.	Lescuraea
203. Plants epiphytic with inconspicuous, creeping, primary stem and erect secondary stems; costa subpercurrent.	Pireella
203. Plants terrestrial and epiphytic, with primary and secondary stems not differentiated; costa ending well below the apex.	204
204. Leaves decurrent; setae rough; capsules inclined; plants largely terrestrial.	Bryhnia
204. Leaves not decurrent; setae smooth; capsules erect; plants epiphytic or saxicolous.	Isothecium
205. Leaf apices rounded-obtuse to truncate.	206
205. Leaf apices acuminate to bluntly acute.	212
206. Leaf apices truncate.	Neckeropsis
206. Leaf apices rounded-obtuse.	207
207. Upper leaf cells less than 3:1.	208
207. Upper leaf cells (not apical ones) more than 5:1.	209
208. Plants strongly complanate, shiny, little altered when moist.	Homalia
208. Plants at best weakly complanate, dull, strongly incurved when dry, erect when moist.	Leptodon
209. Alar cells inflated.	210
209. Alar cells not at all inflated.	211
210. Plants strongly julaceous; leaves concave; occurring in or near streams.	Scleropodium
210. Plants with loosely spreading leaves; leaves only slightly concave; occurring in fens.	Calliergon
211. Costa ending in a spine.	Platyhypnidium
211. Costa not projecting at apex.	Hygrohypnum
212. Upper leaf cells 1-2:1.	213
212. Upper leaf cells more than 5:1.	227
213. Sporophytes terminal on erect branches; upper cells rounded.	214
213. Sporophytes lateral; upper cells rhombic to subquadrate.	217
214. Basal marginal cells short, rounded-quadrate.	215
214. Basal marginal cells elongate.	216
215. Upper leaf cells strongly bulging; leaves lanceolate; calyptrae hairy, mitrate.	Macrocoma
215. Upper leaf cells flat; leaves oblong-lanceolate; calyptrae naked, cucullate.	Drummondia
216. Inner basal leaf cells subquadrate to rounded; calyptrae short, plicate.	Groutiella
216. Inner basal cells linear; calyptrae long, not plicate.	Schlotheimia
217. Costa strongly flexuose above; leaf margins with multicellular teeth.	Herpetineuron
217. Costa straight or faintly flexuose; leaf margins entire to serrulate.	218
218. Costa ending in the leaf apex.	219
218. Costa ending well below the leaf apex.	223
219. Upper leaf cells thick-walled, rounded-quadrate to elliptic.	220
219. Upper leaf cells firm-walled, short-oblong to rhombic.	222
220. Plants with clusters of axillary brood branchlets.	Leskeella
220. Plants without brood branchlets.	221
221. Alar cells extending to the costa; inner basal cells not differentiated; peristome white.	Lindbergia
221. Alar cells restricted in 5-6 rows along the margins, not reaching the costa; inner basal cells long rectangular; peristome yellow.	Pseudoleskeella
222. Costa relatively narrow, less than 35 µm wide at base; plants terretrial.	Amblystegium
222. Costa relatively broad, mostly more than 50 µm at base; plants aquatic.	Hygroamblystegium
223. Plants with secondary stems erect and branched.	224
223. Plants without differentiated secondary stems, prostrate.	225
224. Leaf apices shortly acuminate; leaves more than 1 mm long; plants eastern.	Forsstroemia
224. Leaf apices broadly acute; leaves less than 1 mm long; plants western.	Porotrichum (Bryolawtonia)
225. Leaves acuminate, often homomallous.	Pseudoleskeella
225. Leaves bluntly acute.	226
226. Leaves obliquely asymmetric at tip; exostome teeth cross-striate; plants boreal and arctic.	Myrinia
226. Leaves symmetric; exostome teeth rudimentary; plants of southeastern North America.	Clasmatodon
227. Plants bearing long, deciduous, flagelliform branches.	Pseudocryphaea
227. Plants without flagelliform branches.	228
228. Plants with inconspicuous, creeping primary stems with reduced leaves and erect, leafy secondary stems.	229
228. Plants without differentiated stems.	232
229. Secondary stems mostly unbranched.	Jaegerina
229. Secondary stems irregulary pinnate.	230
230. Costa toothed at back on secondary stem leaves; branch leaves acute.	Bestia
230. Costa smooth at back; branch leaves acuminate.	231
231. Leaf margins revolute nearly throughout, serrate above, often with reflexed teeth; costa often with supplementary costae; western in distribution (disjunct in Newfoundland).	Antitrichia
231. Leaf margins reflexed, entire to serrulate; costa without supplementary costae; eastern in distribution.	Forsstroemia
232. Plants aquatic, coarse; costa broad, more than 100 µm wide at base, bluntly excurrent.	233
232. Plants of various habitats; costa much narrower, ending below the apex to excurrent, if excurrent then finely so.	234
233. Costa about 1/3 the width of the leaf base; the lamina with multistratose streaks.	Donrichardsia
233. Costa about 1/4 the width of the leaf base; the lamina unistratose throughout.	Hygroamblystegium
234. One side of stems for entire length covered by reddish rhizoidal tomentum; leaves strongly plicate.	Tomentypnum
234. Tomentum, if present, restricted to extreme base of stems; leaves plicate or not.	235
235. Leaves falcate-secund.	236
235. Leaves straight.	248
236. Stems with a hyalodermis.	237
236. Stems without a hyalodermis.	239
237. Leaves strongly plicate, distinctly denticulate in upper portion.	Sanionia
237. Leaves striolate to plane, entire to slightly denticulate.	238
238. Alar cells inflated; plants occurring in streams.	Hygrohypnum
238. Alar cells poorly differentiated; plants occurring in rich fens.	Limprichtia
239. Plants of upland habitats; leaves plicate.	Brachythecium
239. Plants of wet habitats; leaves not plicate.	240
240. Leaves keeled, distinctly to obscurely 3-ranked; endostome segments joined at tips.	Dichelyma
240. Leaves not keeled or 3-ranked; endostome segments free.	241
241. Costa excurrent.	242
241. Costa subpercurrent.	244
242. Alar cells poorly differentiated.	Drepanocladus
242. Alar cells abruptly inflated.	243
243. Leaf margins entire.	Drepanocladus
243. Leaf margins finely denticulate.	Warnstorfia
244. Leaf margins finely denticulate at apex.	Warnstorfia
244. Leaf margins entire throughout.	245
245. Plants on rocks in mountain streams.	Hygrohypnum
245. Plants in fens and seeps, not on rocks.	246
246. Cells in lower half of leaf porose; plants of the arctic.	Loeskypnum
246. Cells not porose except at extreme insertion; plants widespread.	247
247. Stems with central strand.	Drepanocladus
247. Stems without central strand.	Hamatocaulis
248. Leaves 3-ranked, conduplicate.	Brachelyma
248. Leaves not 3-ranked or conduplicate.	249
249. Plants pendulous from branches; stem leaves with capillary points; branch leaves recurved; plants restricted to southernmost Florida.	Zelometeorium
249. Plants terrestrial to epiphytic, never pendulous; stem leaves with shorter points; branch leaves mostly not squarrose; plants mostly more northern.	250
250. Leaf cells long hexagonal, less than 8:1.	251
250. Leaf cells linear, more than 10:1.	258
251. Leaves broadly ovate, deeply concave; restricted to Alaska.	Myuroclada
251. Leaves lanceolate to ovate, not or only slightly concave; widespread.	252
252. Plants epiphytic.	253
252. Plants terrestrial and saxicolous.	254
253. Leaf margins entire; leaf apex gradually acuminate; peristome double and reflexed.	Anacamptodon
253. Leaf margins mostly toothed; leaf apex piliferous; peristome single to absent.	Fabronia
254. Leaf apices piliferous.	Fabronia
254. Leaf apices acute to acuminate.	255
255. Upper leaf cells thick-walled, with rounded ends; capsules erect.	Pseudoleskeella
255. Upper leaf cells firm-walled, with pointed ends; capsules inclined.	256
256. Plants on soil in dry habitats, especially prairies.	Brachythecium
256. Plants on logs and soil in mesic to wet habitats.	257
257. Leaves greater than 1 mm long.	Leptodictyum
257. Leaves less than 1 mm long.	Amblystegium
258. Plants attached to rocks in fast-flowing streams and beside waterfalls.	Platyhypnidium
258. Plants in various habitats but not on rocks in fast-flowing water.	259
259. Plants terrestrial, large, coarse, erect; stems pinnately branched.	260
259. Plants various, prostrate to ascending, if erect then in wetlands; branching various.	261
260. Stem leaves ovate-lanceolate, acuminate to filiform, plicate; plants on litter in coniferous forests.	Trachybryum
260. Stem leaves ovate-oblong, abruptly apiculate, not plicate; plants in lawns and gardens.	Pseudoscleropodium
261. Leaves plicate.	262
261. Leaves not plicate.	264
262. Branches curved-ascending when dry.	Homalothecium
262. Branches prostrate.	263
263. Leaf apices coarsely serrate; upper leaf cells thick-walled; alar cells well differentiated, quadrate; plants rigid.	Palamocladium
263. Leaf apices entire to serrulate; upper leaf cells firm-walled; alar cells mostly differentiated, short-rectangular; plants soft.	Brachythecium
264. Plants on tree trunks; calyptrae sparsely hairy; setae rough; plants of eastern U.S..	Homalotheciella
264. Plants not on tree trunks except rarely at bases, if on trees plants of western North America; calyptrae naked; setae usually smooth, rarely rough.	265
265. Plants terete, at least at apex; leaves broadly oblong to ovate, concave to cucullate.	266
265. Plants with spreading leaves; leaves lanceolate, not or scarcely concave.	272
266. Leaves abruptly acuminate.	267
266. Leaves broadly acute to obtuse, sometimes with a minute apiculus.	269
267. Costa with one or more spines at the tip; plants of western North America.	Scleropodium
267. Costa without spines at tip; plants widespread.	268
268. Leaf apex filiform, flat.	Cirriphyllum
268. Leaf apex broader, twisted.	Bryoandersonia
269. Leaves with minute apiculus.	270
269. Leaves not apiculate.	271
270. Plants green; basal leaf cells porose.	Loeskypnum
270. Plants reddish; basal leaf cells not porose.	Sarmentypnum
271. Leaves obtuse; plants occurring in fens and swamps; widespread.	Calliergon
271. Leaves broadly acute; plants occurring on moist rocks and soil; Pacific coast.	Scleropodium
272. Branch leaves with apical cells about 1/2 the length of those at midleaf.	Eurhynchium
272. Branch leaves with apical cells scarcely shorter than those at midleaf.	273
273. Leaf apices twisted; stems often complanate-foliate.	Steerecleus
273. Leaf apices flat; stems rarely complanate-foliate.	274
274. Leaves with channeled leaf apices from a concave base, with a narrow insertion.	Campylium
274. Leaves without channeled leaf apices, the leaf base not concave or with a narrow insertion.	275
275. Alar cells numerous and quadrate with more on one side of the costa than the other, collenchymatous; plants of southernmost Florida.	Entodontopsis
275. Alar cells few, symmetrically arranged, not collenchymatous; plants widespread.	276
276. Branch and stem leaves strongly differentiated; opercula long rostrate.	Eurhynchium
276. Branch and stem leaves scarcely differentiated; opercula conic to apiculate.	277
277. Costa percurrent or nearly so.	278
277. Costa ending well below leaf apex.	279
278. Costa indistinct at midleaf, not toothed; setae smooth; propagula uniseriate, often formed on back of costa at apex.	Conardia
278. Costa distinct throughout, toothed at back above; setae rough; propagula not present.	Brachythecium
279. Leaves wide-spreading with entire margins; stems complanate-foliate, plants occurring in wet habitats.	Leptodictyum
279. Leaves erect to spreading with serrulate margins, rarely entire; stems not complanate-foliate, plants occurring in various habitats.	Brachythecium
280. Capsules large, sessile, asymmetric.	Diphyscium
280. Capsules smaller, usually exserted, symmetric.	281
281. Costa ridged at back.	282
281. Costa smooth or toothed at back, not ridged.	283
282. Leaf cells rounded-oblate.	Dryptodon
282. Leaf cells long-rectangular, more than 5:1.	Dicranum
283. Conspicuous clusters of dark rhizoids obscuring the stem.	284
283. Rhizoids inconspicuous or if obvious, never obscuring the stem.	287
284. Leaf cells strongly unipapillose on both surfaces.	Aulacomnium
284. Leaf cells smooth or prorulose.	285
285. Leaves narrowly lanceolate from an ovate base.	Anacolia
285. Leaves ovate to broadly elliptic.	286
286. Rhizoidal (macronematal) initials in longitudinal rows; endostome fused into a dome.	Cinclidium
286. Rhizoidal initials not in longitudinal rows; endostome segments free.	Rhizomnium
287. Plants blackish, occurring on wet rocks usually near streams or the sea, never with propagula.	288
287. Plants greenish, occurring in various habitats, rarely on wet rocks by streams, with or without propagula.	290
288. Leaf bases with submarginal band of elongate cells.	Scouleria
288. Leaf bases without differentiated submarginal cells.	289
289. Leaf margins incurved.	Grimmia
289. Leaf margins plane to recurved.	Schistidium
290. Hyaline basal cells extending up the margins farther than at the costa, forming a V-shaped area.	291
290. Hyaline basal cells if present extending more or less equally up the margins as costa or farther up the costa.	293
291. Upper cells bulging but not papillose.	Luisierella
291. Upper cells pluripapillose.	292
292. Leaves squarrose-recurved from an erect base when moist; leaf margins serrulate above; sporophytes lateral.	Pleurochaete
292. Leaves erect-spreading to spreading from an erect base when moist; leaf margins entire to notched; sporophytes terminal.	Tortella
293. Plants glaucous, bluish-green.	Saelania
293. Plants not glaucous or bluish.	294
294. Leaves bordered by 2 or more rows of elongate cells.	295
294. Leaves unbordered or if bordered then by only a single row of somewhat elongate cells, or by short cells.	309
295. Leaf margins entire.	296
295. Leaf margins toothed, sometimes obscurely so.	300
296. Leaf cells longer than 3:1.	297
296. Leaf cells 1-2:1.	298
297. Leaf cells in oblique rows; leaves rounded-obtuse, bluntly apiculate.	Pseudobryum
297. Leaf cells not in obvious rows; leaves various.	Bryum
298. Rhizoidal (macronematal) initials in longitudinal rows; endostome fused to a dome.	Cinclidium
298. Rhizoidal initials not in longitudinal rows; endostome segments free.	299
299. Leaves bluntly acute; border unistratose; stems blackish; stomates superficial.	Cyrtomnium
299. Leaves emarginate, rounded-apiculate; border various; stems reddish; stomates immersed.	Rhizomnium
300. Leaves lanceolate from an expanded base, the base with numerous, abruptly hyaline cells.	Syrrhopodon
300. Leaves without expanded base, without hyaline cells.	301
301. Leaf margins with paired teeth.	302
301. Leaf margins with single teeth.	304
302. Leaf cells strongly bulging.	Trachycystis
302. Leaf cells flat.	303
303. Some leaves with low, inconspicuous lamellae; costa in transverse section with two stereid bands; peristome of 32 small teeth attached at tips to a tympanum.	Atrichum
303. No leaves with lamellae; costa with or without a single stereid band; exostome of 16 free teeth.	Mnium
304. Leaves rugose wet or dry; plants restricted to Pacific Northwest.	Roellia
304. Leaves flat when wet, contorted but not rugose when dry; plants widespread.	305
305. Leaf cells shorter than 2:1.	Plagiomnium
305. Leaf cells 3:1 or more.	306
306. Stems rosulate-foliate, occurring erect from a horizontal underground stem; sporophytes often clustered.	Rhodobryum
306. Stems foliate throughout, without rhizome-like connections between erect stems; sporophytes not clustered.	307
307. Leaf cells in oblique rows; leaves rounded-obtuse, apiculate.	Pseudobryum
307. Leaf cells not in obvious rows; leaves broadly acute to acuminate.	308
308. Capsules erect and symmetric; endostome with a high basal membrane, segments lacking or rudimentary, cilia absent.	Brachymenium
308. Capsules inclined and asymmetric; endostome with a keeled basal membrane, keeled and perforate segments, and usually with cilia.	Bryum
309. Leaf margins with paired teeth.	310
309. Leaf margins with single teeth or entire.	315
310. Leaf bases with abruptly differentiated colorless cells (cancellinae); propagula borne on costa near apex.	Syrrhopodon
310. Leaf bases without cancellinae; propagula absent.	311
311. Leaf cells smooth.	312
311. Leaf cells prorulose or with fine cuticular ridges.	313
312. Leaves elliptic to ovate-elliptic.	Mnium
312. Leaves linear-lanceolate.	Pyrrhobryum
313. Upper leaf cells with cuticular ridges; stems triangular in transverse section.	Plagiopus
313. Upper leaf cells prorulose; stems round in transverse section.	314
314. Leaves crispate when dry.	Bartramia
314. Leaves straight when dry.	Philonotis
315. Leaf cells strongly bulging on one or both surfaces, not papillose.	316
315. Leaf cells flat, smooth or papillose, or if bulging then papillose.	318
316. Leaf laminae bistratose.	Timmiella
316. Leaf laminae unistratose.	317
317. Plants with sheathing leaf bases.	Timmia
317. Plants without sheathing leaf bases.	Bryobrittonia
318. Leaves with abruptly expanded, sheathing leaf bases.	319
318. Leaves with leaf bases not or only gradually expanded, rarely sheathing.	326
319. Leaf cells papillose (at least on sheath) or prorulose.	320
319. Leaf cells smooth.	321
320. Leaf cells papillose over the lumina.	Timmia
320. Leaf cells prorulose.	Bartramia
321. Upper leaf cells quadrate.	322
321. Upper leaf cells short-rectangular.	323
322. Capsules inclined and asymmetric, strumose; plants widespread.	Oncophorus
322. Capsules erect, symmetric, not strumose; plants restricted to southwestern U.S..	Symblepharis
323. Awns roughened throughout by projecting cell ends.	Trichodon
323. Awns smooth or only rough at apex.	324
324. Capsules with neck as long as or longer than the urn.	Trematodon
324. Capsules with neck much shorter than the urn.	325
325. Capsules erect, cylindric, smooth; peristome teeth irregularly perforate or deeply cleft into terete, sometimes filiform divisions.	Ditrichum
325. Capsules inclined, oblong, smooth or furrowed, if erect then furrowed; peristome teeth flat, split 1/2 way down, vertically pitted.	Dicranella
326. Alar cells enlarged, colored, or inflated.	327
326. Alar cells scarcely differentiated.	333
327. Upper and median leaf cells with coarse, irregular cuticular ridges, resembling papillae in transverse section; capsules cylindric, smooth, erect.	328
327. Leaf cells without cuticular ridges; capsules various.	329
328. Leaves with clusters of spherical propagula at leaf apex; leaf margins bistratose.	Grimmia
328. Leaves without propagula; leaf margins unistratose.	Dicranoweisia
329. Costa with 2 stereid bands.	Dicranum
329. Costa without stereids.	330
330. Capsules curved, strumose; plants on alpine rocks.	Kiaeria
330. Capsules erect, not strumose; plants widespread.	331
331. Capsules cylindric; plants usually terrestrial or on tree trunks, rarely on rock.	Dicranum
331. Capsules short, obovoid to pyriform; plants on rocks.	332
332. Capsules ribbed when dry; peristome vertically pitted-striolate below.	Arctoa
332. Capsules smooth when dry; peristome papillose.	Blindia
333. Leaf cells smooth.	334
333. Leaf cells papillose or prorulose.	398
334. Asexual propagula borne on the leaf surfaces.	Rhachithecium
334. Asexual propagula absent, axillary or on leaf apices or specialized structures.	335
335. Leaves ovate to obovate, broadly obtuse, with the costa ending below the leaf apex	336
335. Leaves linear, ovate-lanceolate, ligulate to ovate, acuminate to acute or awned, with costa ending below the apex to excurrent..	342
336. Leaf apices cucullate.	Globulinella
336. Leaf apices not cucullate.	337
337. Plants with large, multicellular propagula in leaf axils; leaves obovate, with cilia on the basal margins.	Oedipodium
337. Plants without axillary propagula; leaves ovate to spatulate, eciliate.	338
338. Plants small and bulbiform, on dry soil; leaves concave and imbricate.	Stegonia
338. Plants small to medium-sized, never bulbiform, on moist soil; leaves flat to concave, mostly not imbricate.	339
339. Leaf cells short-rectangular, lax, thin-walled; capsules erect.	340
339. Leaf cells long-hexagonal, firm-walled; capsules inclined to horizontal.	341
340. Apical marginal leaf cells short-rhombic, oblong- hexagonal internally; capsules without a distinct neck; plants of southern United States.	Splachnobryum
340. Apical marginal leaf cells laxly rectangular, similar to internal ones; capsules with well differentiated neck; plants northern.	Tayloria
341. Plants whitish-green, terete; upper leaf cells long, 7-9:1.	Anomobryum
341. Plants reddish or green, not terete; upper cells shorter, 2-6:1.	Bryum
342. Leaves oblong, lingulate to ovate.	343
342. Leaves lanceolate to linear.	368
343. Leaf cells rounded to quadrate, more or less isodiametric.	344
343. Leaf cells short-rectangular to linear.	353
344. Leaf bases with abruptly differentiated, hyaline cells (cancellinae); leaf apices often with propagula.	Calymperes
344. Leaf bases without cancellinae although sometimes gradually hyaline; leaf apices without propagula.	345
345. Costa excurrent to ending in the cusp; leaf apex cuspidate to piliferous.	346
345. Costa subpercurrent; leaf apex broadly acute or obtuse to rarely mucronate.	349
346. Leaf apices piliferous.	Desmatodon
346. Leaf apices cuspidate.	347
347. Plants with rhizoidal tubers, known only from Louisiana; capsules unknown.	Tortula (Chenia)
347. Plants lacking tubers, widespread in the north; capsules exserted.	348
348. Capsules 0.4-0.8 mm long, obovoid; spores more than 20 µm in diameter; peristome absent or rudimentary; plants boreal-temperate.	Pottia
348. Capsules 2.5-3.5 mm long, cylindric; spores less than 20 µm in diameter; peristome well developed with twisted teeth from a basal membrane; plants of tundra.	Crumia
349. Peristome teeth four; propagula cups borne on apices of sterile shoots.	Tetraphis
349. Peristome teeth 16; propagula cups absent.	350
350. Leaves homomallous, broadly oblong to oblong- ovate, subacute to obtuse.	Aulacomnium
350. Leaves not homomallous, oblong to lanceolate, mucronate to acuminate.	351
351. Leaves broadly to narrowly lanceolate; peristome double.	Meesia
351. Leaves broadly oblong to spatulate; peristome single.	352
352. Costa in transverse section with 2 stereid bands.	Barbula
352. Costa in transverse section with 1 stereid band.	Scopelophila
353. Plants filiform, julaceous (if costa not excurrent see also Anomobryum).	Aongstroemia
353. Plants coarser, not julaceous.	354
354. Capsules horizontal to pendulous.	355
354. Capsules erect.	360
355. Capsules curved, asymmetric.	356
355. Capsules straight, symmetric.	357
356. Exostome shorter than and alternate with endostome.	Plagiobryum
356. Exostome longer than and opposite to endostome.	Funaria
357. Capsules ovate, less than 1 mm long; stomates none; endostome fused to exostome, cilia none.	Discelium
357. Capsules cylindric to ovate, usually greater than 1 mm long; stomates present; endostome free of exostome, cilia mostly present.	358
358. Leaf cells in oblique rows.	Plagiobryum
358. Leaf cells not in obvious oblique rows.	359
359. Leaf cells 4:1 or less.	Bryum
359. Leaf cells 5:1 or longer.	Pohlia
360. Peristome absent.	361
360. Peristome present.	363
361. Calyptrae 4-angled, sheathing the entire capsule until after dehiscence.	Pyramidula
361. Calyptrae not angled, not sheathing or persistent.	362
362. Capsules subcylindric or narrrowly pyriform; annuli none; exothecial cells oblong to oblong-linear; calyptrae inflated- cucullate.	Entosthodon
362. Capsules urceolate to broadly pyriform; annuli present; exothecial cells irregularly hexagonal; calyptrae inflated-mitrate.	Physcomitrium
363. Peristome of endostome only, without a center line on the outer surface.	Mielichhoferia
363. Peristome double or of exostome only, with a center line on the outer surface.	364
364. Plants with scarcely differentiated neck.	365
364. Plants with well-differentiated neck (apophysis).	366
365. Plants of arctic tundra.	Funaria
365. Plants of British Columbia (50° N) and south.	Entosthodon
366. Urns black, sometimes with yellow apophyses.	Tetraplodon
366. Urns and apophyses green to brown.	367
367. Setae pale greenish-white, slender; costa filling the acumen; plants of eastern North America.	Splachnum
367. Setae brownish, stout to slender; costa ending below the leaf apex; plants of western and northern North America.	Tayloria
368. Leaves conspicuously 4-ranked.	Conostomum
368. Leaves not conspicuously ranked (if 3-ranked see Meesia).	369
369. Leaf cells short, 1(-2):1, rounded to quadrate.	370
369. Leaf cells long, (3-)4:1 or longer, rectangular to long-hexagonal.	386
370. Perichaetial leaves strongly differentiated, with an awn as long as the lamina; leaves bistratose.	Diphyscium
370. Perichaetial leaves slightly or not differentiated, never long awned; leaves uni- to multistratose.	371
371. Capsules distinctly 8 or 16 ribbed and furrowed.	372
371. Capsules smooth or indistictly furrowed when dry but without distinct ribs.	378
372. Calyptrae mitrate.	373
372. Calyptrae cucullate.	375
373. Calyptrae hairy.	Ulota
373. Calyptrae naked.	374
374. Annuli none; calyptrae plicate.	Orthotrichum
374. Annuli compound; calyptrae not plicate.	Brachydontium
375. Setae cyneous; plants rare, forming tight cushions on alpine slopes.	Oreas
375. Setae erect (but sometimes twisted); plants various but not as above.	376
376. Capsules abruptly bent at the seta-capsule junction and horizontal, often becoming purple-red when mature.	Ceratodon
376. Capsules erect to suberect and becoming brown when mature.	377
377. Peristome teeth divided to half their length; capsules cylindric to ovate-cylindric, ca. 2 mm long; plants of Pacific Northwest.	Cynodontium
377. Peristome teeth undivided; capsules ovoid, less than 1 mm long; plants of eastern and midwestern U.S. and maritime Canada.	Rhabdoweisia
378. Capsules with an erect, elongate, well defined neck; peristome double.	Meesia
378. Capsules with a short, inconspicous neck; peristome single.	379
379. Capsules inclined.	380
379. Capsules erect.	381
380. Capsules less than 1 mm long, black, not strumose; leaf margins unistratose; plants of rich fens.	Catoscopium
380. Capsules 1.5-2.0 mm long, pale, strumose; leaf margins bistratose; plants on moist soil, rocks and logs.	Oncophorus
381. Capsules immersed to short-exserted.	Grimmia
381. Capsules long-exserted.	382
382. Calyptrae mitrate.	383
382. Calyptrae cucullate, not plicate.	384
383. Calyptrae plicate; setae straight.	Ptychomitrium
383. Calyptrae not plicate; setae cygneous.	Campylostelium
384. Costa with 1 stereid band; leaf margins bistratose.	Trichostomopsis
384. Costa with 2 stereid bands; leaf margins unistratose.	385
385. Leaves lanceolate from a somewhat expanded base.	Didymodon
385. Leaves oblong.	Barbula
386. Leaves subulate.	387
386. Leaves acute to acuminate.	394
387. Capsules curved and asymmetric.	Dicranella
387. Capsules straight, symmetric, although sometimes inclined to pendulous.	388
388. Setae flexuose-curved to cygneous.	389
388. Setae straight, but sometimes spirally- twisted.	391
389. Setae more 10 mm long; plants more than 5 mm tall; leaves more than 4 mm long; capsules pyriform.	Leptobryum
389. Setae less than 5 mm long; plants less than 3 mm tall; leaves less than 2 mm long; capsules hemispheric.	390
390. Plants ephemeral, on soil in Florida; setae stout curved at apex, not twisted; capsules eperistomate.	Eccremidium
390. Plants perennial, on rock, not in Florida; setae slender, twisted; capsules peristomate.	Seligeria
391. Peristome double; plants arctic.	Pseudoditrichum
391. Peristome single; plants widespread.	392
392. Capsules ovoid; plants on calcareous rocks.	Seligeria
392. Capsules oblong to cylindric; plants generally on soil.	393
393. Capsules long cylindric; peristome teeth divided to base, terete, papillose.	Ditrichum
393. Capsules short cylindric; peristome teeth divided half their length, flat, vertically pitted- striolate.	Dicranella
394. Costa occupying 1/2 or more of leaf base; capsules curved and asymmetric, elongate-pyriform from a neck as long as the urn.	Amblyodon
394. Costa occupying less than 1/4 the leaf base; capsules straight and symmetric, without conspicuous neck.	395
395. Plants small, less than 2 mm high, gregarious, occurring on calcareous rocks; capsules ovate.	Seligeria
395. Plants larger, mostly more than 5 mm, in tufts occurring on various substrates; capsules cylindric.	396
396. Leaves flexuose-twisted when dry; capsules erect; plants occurring in the southern Appalachians and California.	Orthodontium
396. Leaves erect, little altered when dry; capsules erect or inclined; plants widespread.	397
397. Capsules terminal, inclined to pendent; peristome double; leaves usually more than 1 mm long, sometimes with axillary propagula.	Pohlia
397. Capsules appearing lateral, erect; peristome single; leaves less than 1 mm long, never with propagula.	Mielichhoferia
398. Leaves bistratose throughout, ligulate to oblong, obtuse; perichaetial leaves long awned.	Diphyscium
398. Leaves unistratose, or if bistratose then not ligulate to oblong; perichaetial leaves not so differentiated.	399
399. Leaf cells rectangular, prorulose; capsules globose, rugulose to furrowed when dry.	400
399. Leaf cells rounded-quadrate; uni- to pluripapillose; capsules ovate to cylindric, smooth or furrowed.	403
400. Leaves strongly ranked.	Conostomum
400. Leaves not conspicuously ranked.	401
401. Capsules erect, or if pendent then from curvature of seta, symmetric, rugulose when dry; peristome reduced to a low membrane.	Bartramidula
401. Capsules strongly inclined, asymmetric, furrowed; peristome better developed.	402
402. Leaves unistratose; plants on soil and rocks in at least periodically wet habitats, often with innovative branches beneath inflorescences.	Philonotis
402. Leaves bistratose at least at margins; plants on banks and cliffs in mesic habitats, without innovative branches.	Bartramia
403. Leaf cells appearing papillose from slightly thickened walls between cells (not prorulose).	404
403. Leaf cells papillose over the lumina.	405
404. Leaves crispate when dry; capsules long exserted, cylindric; plants usually occurring on logs.	Dicranoweisia
404. Leaves erect, straight to curved; capsules immersed to short exserted, ovate-cylindric; plants occurring on rocks.	Grimmia
405. Leaf cells collenchymatous and stellate.	406
405. Leaf cells not thickened in the corners or if so merely rounded and not stellate.	407
406. Leaf cells unipapillose; leaves not recurved.	Aulacomnium
406. Leaf cells pluripapillose; leaves recurved.	Geheebia
407. Leaves with abruptly differentiated hyaline cells occupying most of the leaf base (cancellinae) and with an intramarginal border of elongate cells (teniolae), at least in lower part of leaf; usually with propagula on leaf apex.	Calymperes
407. Leaves without cancellinae, or if present then never with teniolae; propagula never on leaf apices but sometimes elsewhere on leaves or in axils.	408
408. Plants with propagula borne terminally on specialized stalks from stem apices.	Aulacomnium
408. Plants with or without various means of asexual reproduction but these never borne on stalks from the stem apices.	409
409. Plants occurring on tree trunks or bare rock, with immersed to shortly exserted, often ribbed capsules.	410
409. Plants usually occurring on soil, if on rocks or trees then capsules long exserted and mostly unribbed (or plants sterile).	412
410. Calyptrae cucullate, not plicate, naked; occurring on wet rocks.	Amphidium
410. Calyptrae mitrate, plicate, usually hairy; occurring on tree trunks and dry rocks.	411
411. Leaves usually crispate to contorted when dry; basal marginal cells with thickened transverse walls; stomates superficial; capsules shortly exserted.	Ulota
411. Leaves usually little altered when dry; basal marginal cells not differentiated; stomates immersed or superficial; capsules immersed to shortly exserted.	Orthotrichum
412. Costa in transverse-section more or less homogeneous, without differentiated stereids.	413
412. Costa in transverse-section with differentiated stereid bands.	417
413. Leaf cells with C-shaped papillae; leaves broadly spatulate.	Gymnostomiella
413. Leaf cells with simple, conic papillae; leaves various but not broadly spatulate.	414
414. Upper leaf cells with 4-7 small, conic papillae.	Zygodon
414. Upper leaf cells with 3 or fewer, simple to branched papillae.	415
415. Leaves less than 0.6 mm long, ligulate, rounded- obtuse; rare plants of calcareous rocks; annuli of 2-3 rows of well-differentiated cells.	Gyroweisia
415. Leaves more than (0.7-)1.5 mm long, lanceolate to ovate, acuminate to obtuse; annuli poorly differentiated.	416
416. Leaves typically crispate to contorted when dry; basal marginal cells with thickened transverse walls; capsules shortly exserted; calyptrae hairy.	Ulota
416. Leaves usually little altered when dry; basal marginal cells not differentiated; capsules immersed to shortly exserted; calyptrae naked (species with contorted leaves) to hairy (species with unaltered leaves).	Orthotrichum
417. Costa with a single, dorsal stereid band.	418
417. Costa with both dorsal and ventral stereid bands.	429
418. Calyptrae campanulate-mitrate, covering entire capsule, often lobed at base; basal leaf cells with thickened transverse walls.	Encalypta
418. Calyptrae cucullate, covering only operculum and capsule apex, unlobed at base; basal leaf cells usually without thickened transverse walls.	419
419. Leaves linear-lanceolate to lanceolate, never with hair points; leaf margins recurved to plane; leaf cells with papillae conic, clavate or branched, rarely C-shaped.	420
419. Leaves broadly lanceolate (from revolute leaf margins), lingulate or oblong-ovate, sometimes with hair points; leaf margins recurved to strongly revolute; leaf cells with papillae stellate from a stipitate base to C-shaped.	424
420. Leaf cells with 4-7 widely spaced, small, conic papillae; elliptic propagula present in leaf axils; peristome double; plants usually occurring on trees, rarely on rock.	Zygodon
420. Leaf cells with 1-3(-4) closely set, simple to branched papillae; propagula absent; peristome single or absent; plants occurring on soil and rocks.	421
421. Leaf margins serrulate above; capsules erect to inclined, often furrowed and strumose; peristome vertically pitted-striolate.	Cynodontium
421. Leaf margins entire; capsules erect, never furrowed or strumose; peristome, when present, papillose.	422
422. Basal leaf cells lax and hyaline; upper leaf margins bistratose throughout; peristome present.	Trichostomopsis
422. Basal leaf cells firm-walled, pale but not hyaline; upper leaf margins unistratose or irregularly bistratose; peristome absent.	423
423. Stem monopodially branched; archegonia on short, lateral branches; stem transverse section rounded- triangular.	Anoectangium
423. Stem sympodially branched; archegonia terminal on main stem; stem transverse section round.	Gymnostomum
424. Leaves with an intramarginal band of enlarged, smooth, often orange cells.	Crumia
424. Leaves without differentiated intramarginal cells but sometimes with smooth marginal cells, these not enlarged.	425
425. Leaves narrowly lanceolate; leaf margins erect and bistratose.	Trichostomopsis
425. Leaves oblong, lingulate to ovate; leaf margins plane to revolute, unistratose or if bistratose then always revolute.	426
426. Upper leaf margins broadly revolute to spirally revolute, with cells often more strongly chlorophyllose than median cells.	Pseudocrossidium
426. Upper leaf margins plane to revolute, with cells undifferentiated or paler than median cells.	427
427. Leaves unbordered; peristome none or rudimentary.	Pottia
427. Leaves often bordered by smooth cells; peristome present.	428
428. Peristome teeth united in a high or rarely low, tubular basal membrane, spirally twisted above; cells of adaxial (upper) surface of costa similar to or smaller than laminal cells in transverse section.	Tortula
428. Peristome teeth free or rarely united in a low basal membrane, erect to slightly twisted above; cells of adaxial surface of costa mostly larger than or otherwise differentiated from laminal cells in transverse section.	Desmatodon
429. Leaf margins abruptly serrate at the shoulder.	Eucladium
429. Leaf margins entire at shoulders.	430
430. Leaf cells with numerous (more than 7), minute, elliptic papillae over the walls as well as the lumina.	Amphidium
430. Leaf cells with fewer than 7, larger, round papillae only over the lumina.	431
431. Leaf margins toothed above.	432
431. Leaf margins entire or roughened with projecting papillae.	436
432. Laminae bistratose; margins unistratose.	Rhexophyllum
432. Laminae unistratose; margins uni- or bistratose.	433
433. Leaf cells bulging, mamillose to unipapillose.	Dichodontium
433. Leaf cells plane, pluripapillose.	434
434. Stems with central strand.	Bryoerythrophyllum
434. Stems without central strand.	435
435. Stems with hyalodermis; adaxial (upper) surface of costa with enlarged, papillose epidermal cells.	Paraleptodontium
435. Stems without hyalodermis; adaxial surface of costa with small, smooth cells.	Leptodontium
436. Leaves at extreme apex with large, curved, projecting papillae.	Dichodontium
436. Leaves at extreme apex with margins entire or papillose-crenulate.	437
437. Stems triquetrous, especially when moist; leaf cells unipapillose, the papillae sometimes branched; plants of California.	Triquetrella
437. Stems without ranked leaves; leaf cells pluripapillose; plants widespread.	438
438. Stems without central strand, in transverse section with largest cells in middle of section.	Oxystegus
438. Stems with central strand, or if poorly developed in transverse section at least with largest cells not in middle of stem.	439
439. Leaf margins plane to erect.	440
439. Leaf margins recurved to revolute, at least near midleaf or below.	443
440. Stems with hyalodermis.	Trichostomum
440. Stems without hyalodermis, epidermal cells small.	441
441. Leaf apices subtubulose; upper leaf cells with 1-2 large, centered, multiplex papillae.	Tuerckheimia
441. Leaf apices flat; upper leaf cells with 3-6 small, scattered, simple, blunt papillae.	442
442. Perichaetia and sporophytes lateral; leaves 2.2-3.0 mm long; axillary hairs of 15-20 cells.	Molendoa
442. Perichaetia and sporophytes terminal; leaves less than 2.0 mm long; axillary hairs of 8-10 cells.	Gymnostomum
443. Peristome none; leaves recurved only on one side.	Hymenostylium
443. Peristome usually present; leaves recurved on both sides.	444
444. Axillary hairs with a brown, slender basal cell; laminal cells well defined in surface view; leaves usually lanceolate; cells of abaxial (back) surface of costa quadrate to short-oblong, rarely elongate; basal laminal cells usually little differentiated, green and short-rectangular.	Didymodon
444. Axillary hairs with all cells hyaline; laminal cells obscure in surface view; leaves usually ovate to oblong; cells of abaxial surface of costa oblong to elongate; basal laminal cells usually strongly differentiated, hyaline and elongate.	Barbula