Section 1. Plants whitish, laminal cells alternating or layered between leucocyst and chlorocyst cells.

Plants whitish, occasionally reddish or purplish tinged; laminal cells differentiated, alternating or layered between hyaline cells (leucocysts) and green cells (chlorocysts).

1. Plants typically of boggy or seepy sites; forming a compact head of clustered short branches (capitulum), below capitulum stems with short to elongate fasciculate branches; leaves of stem and branch dimorphic; in cross-section lamina unistratose, cells alternating between chlorocysts and leucocysts
Sphagnaceae
1. Plants of moist to semi-dry sites, often lignicolous or epiphytic; stem and branch leaves monomorphic, mostly evenly distributed along stems; in cross-section lamina bi- to multistratose, chlorocysts layered between 1 or more layers of leucocysts above and below
2
2. Leaves appear singly costate, costal stereids forming a rib on the abaxial (back) side of leaf
Calymperaceae p.p.
2. Leaves apparently ecostate, lacking a central rib of stereids
Leucobryaceae


Section 2. Upper distal surface of leaves with rows of lamellae or short filaments.

1. Lamellae in long continuous rows, occasionally rows few or discontinuous; peristome teeth 16, 32 or 64, entire, usually with tips of teeth attached to an epiphragm
1. Lamellae forming short rows or occurring as short filaments scattered over surface; peristome of 16 teeth, often perforate or divided
2
2. Distal upper surface covered by filaments, often papillose, if with lamellae then leaves ovate with margins plane; calyptra cucullate
Pottiaceae p.p.
2. Distal upper surface covered by rows of lamellae, with leaf margins erect to incurved; calyptra campanulate, lobed at base
Grimmiaceae p.p.

PLANTS ACROCARPOUS

Plants acrocarpous, stems mostly erect or occasionally spreading, solitary or in short to tall loose or dense tufts; sporophytes terminal on stems or branched innovations; peristome single or double, rarely absent.


Section 3. Plants acrocarpous. Leaves arranged in 2 ranks (distichous) or in 4 ranks but appearing 2-ranked.


1. Leaf costa long excurrent, 2-3 times longer than lamina length; lower and basal cells linear-rectangular; confined to high, dry areas
Ditrichaceae p.p.
1. Leaf costa subpercurrent to short excurrent (rarely long excurrent), lower and basal cells quadrate to rectangular; lowland to high montane
2
2. Leaves exhibiting an extended dorsal and ventral lamina from a sheath-like leaf base (vaginant laminae)
2. Leaves lacking an extended dorsal and ventral lamina from a sheath-like base
3
3. Leaves folded, conduplicate
4
3. Leaves flat, not folded; laminal cells smooth
5
4. Laminal cells pluripapillose; leaves short oblong-ovate, less than 1 mm long
4. Laminal cells smooth; leaves oblong-lanceolate, mostly 2-3 mm
5. Stems spreading or creeping; leaves elliptical, bordered
5. Stems erect; leaves ovate, lacking a bordered


Section 4. Plants acrocarpous. Leaves in 3 or more rows. Laminal cells papillose or mammillose (cells often isodiametric or shortly elongate).


1. Basal portion of leaf exhibiting a cancellinae (enlarged clear cells), strongly differentiated from basal margin and distal cells; marginal or intramarginal border often present; laminal cells above isodiametric, gemmae nearly always present on leaves, particularly leaf tips; plants mostly epiphytic
Calymperaceae p.p.
1. Basal portion of leaf lacking a cancellinae, cells either similar to distal cells or gradually differentiated toward base, if differentiated then leaf border lacking; gemmae absent from leaves
2
2. Leaves ecostate; mostly on rocks
3
2. Leaves costate; on various substrate including rocks
4
3. Leaf margins plane; laminal cells unipapillose on back; plants small, deep dark red or blackish, in montane areas; capsules opening by 4 (division throughout) or 8 (distal tip) slits or valves
3. Leaf margins recurved; laminal cells 1-several papillose, papillae in a row; plants medium sized, dark green to brown, or greyish; mid-montane; capsules operculate, lacking a peristome
4. Leaves completely to partially bistratose distally
5
4. Leaves unistratose or only partially bistratose, particularly restricted to margins
8
5. Peristome teeth of 16 teeth in 8 pairs; leaves spathulate, apex acute to apiculate
5. Peristome teeth of 16 unpaired teeth; leaves mostly ovate-lanceolate to lanceolate, if spathulate then costa excurrent
6
6. Laminal cells subquadrate to short rectangular, appearing bipapillose
Ditrichaceae p.p.
6. Laminal cells rounded, mammillose
7
7. Leaf margins uni-, bi- or tristratose; perichaetial leaf costa long excurrent with distal lamina erose or fimbriate; sporophytes immersed; seta short; capsules strongly asymmetric, obliquely and broadly ovoid below, narrow toward mouth; peristome double; plants found on rock or soil
Diphysciaceae
7. Leaf margins bistratose, sometimes incomplete below; perichaetial leaf costae subpercurrent; sporophytes exserted; seta elongate; capsules symmetric; peristome single; plants exclusively found on rocks
Grimmiaceae p.p.
8. Laminal cells stellate, unipapillose, papillae over cell lumen; basal cells inflated; leaf margins recurved nearly throughout; distal stems naked with a few highly reduced leaves; plants of marshes and bogs at high elevations
8. Laminal cells not stellate, uni- to pluripapillose; basal cells not conspicuously inflated; lacking specialised distal branches or stems (sometimes with deciduous leaves); plants mostly of semi-wet or dry sites
9
9. Laminal cells narrowly to somewhat broadly rectangular with projecting papillae at cell ends (rarely single over cell lumen); leaf margins often coarsely toothed, teeth single or more often double; capsules subglobose, inclined or if erect then immersed
Bartramiaceae
9. Laminal cells mostly isodiametric or short rectangular; papillae mostly over cell lumina or cells mammillose; leaf margins entire, crenulate or a few teeth at apex; capsules ovoid to cylindrical
10
10. Laminal cells often bipapillose; capsules immersed to shortly exserted; peristome double or reduced; calyptra campanulate, plicate or not, hairy or naked; epiphytic or rarely on rocks
10. Laminal cells uni- or pluripapillose, or mammillose; capsules mostly long, rarely short exserted; calyptra cucullate or if campanulate then long cylindrical, smooth; mostly terrestrial, occasionally epiphytic
11
11. Leaves bordered by few to several rows of hyaline cells, border extending 1/3 from base to near apex; laminal cells uni-, bi- or pluripapillose; alar cells well differentiated
11. Leaves lacking a border; cells variously ornamented; alar cell undifferentiated
12
12. Leaves differentiated, base clasping, limb spreading; plants of wet or moist sites
13
12. Leaves undifferentiated, or if not, then base not clasping stem or if clasping upper laminal cells pluripapillose
14
13. Laminal cells subquadrate, mammillose; costa percurrent
Ditrichaceae p.p.
13. Laminal cells short-rectangular, rounded, papillae projecting at cell ends; costa short excurrent
14. Leaf costa in cross-section little differentiated, well developed stereid band lacking

15
14. Leaf costa in cross-section usually well developed, stereid band present, only below guide cells or both above and below

17
15. Laminal cells mammillose or weakly unipapillose, cells crowded, little space between cell lumens
15. Laminal cells pluripapillose, cells widely spaced, or if crowded, papillae extending between cell lumens
16
16. Leaves spathulate or if narrowly oblong-lanceolate then hyaline basal cells extending upward along margin a short distance; peristome single, teeth 16 in 8 pairs
16. Leaves narrowly lanceolate to oblong- or ovate-lanceolate, basal cells uniform across; peristome double or variously reduced, teeth 16 separated or in 8 pairs

17. Capsules cleistocarpic, immersed, globose to oval

17. Capsules stegocarpic, exserted
18
18. Calyptrae long cylindrical-campanulate; leaves oblong-elliptic to -obovate, laminal cells coarsely pluripapillose, papillae usually branched; usually restricted to high elevations Encalyptaceae
18. Calyptra cucullate; leaves of various shapes; laminal cells uni- to pluripapillose, simple or branched; plants found in all zones Pottiaceae p.p.

Section 5. Plants acrocarpous. Leaves in 3 or more rows, ranked or not. Laminal cells smooth.


1. Plants minute, ephemeral or not; leaves costate or ecostate, capsules cleistocarpous or gymnostomous, mostly immersed 2
1. Plants conspicuous, mostly medium sized to large, not ephemeral; leaves costate; capsules stegocarpous or rarely gymnostomous, mostly long exserted 7
2. Laminal cell walls firm, mostly rectangular to subquadrate 3
2. Laminal cell walls lax, short- to long-rhomboidal or hexagonal-rhomboidal 6
3. Leaves oblong to obovate or orbicular, margins entire; annulus well developed Rhachitheciaceae p.p.
3. Leaves mostly lanceolate, if obovate then distal leaf margins usually crenulate or weakly serrulate; annulus absent or well developed 4
4. Spores very large, few Archidiaceae
4. Spores small, numerous 5
5. Capsules with an elongate neck, often half or more the length of capsule, stomata often numerous in neck region Bruchiaceae p.p.
5. Capsules with an inconspicuous neck or neck lacking, stomata few or absent Ditrichaceae p.p.
6. Stems fleshy, partially subterranean; capsules wrinkled or warty, if smooth then exserted and leaves ecostate Gigaspermaceae
6. Stems from a persistent protonema, not subterranean; capsules smooth or weakly bulging-mammillose, immersed Ephemeraceae
7. Laminal cells narrowly rectangular and strongly sinuose throughout except at basal margin; plants found exclusively on rocks Grimmiaceae p.p.
7. Laminal cells not sinuose throughout, walls entire, or if sinuose not strongly so and restricted in distribution, not throughout; plants found on various substrates including rocks 8
8. Leaf margins bordered, border extending to apex or ending somewhat below, adjacent inner laminal cells large, often hexagonal-elongate to broadly fusiform or rhomboidal 9
8. Leaf margins lacking a border, or if bordered then confined to leaf base; marginal cells similar to or only slightly differentiated from inner laminal cells 12
9. Laminal cells subquadrate and rounded to oblong-oval, distally obliquely arranged Mniaceae p.p.
9. Laminal cells rhombic to elongate-hexagonal, not obliquely arranged 10
10. Leaf border consisting of long linear cells; capsules often inclined to pendulous Bryaceae p.p.
10. Leaf border consisting of large, rectangular to fusiform cells; capsules erect, if inclined or subpendulous then seta hygroscopic 11
11. Capsules with a conspicuously modified, enlarged neck, often inflated or larger than urn; peristome single, 16 teeth united in pairs, or teeth 8, often recurved when dry; plants usually epiphytic, on dung or decaying plant material Splachnaceae p.p.
11. Capsules with an inconspicuous or narrowed neck; peristome absent, single and represented by an exostome of 16 teeth, or double, teeth incurved when wet; plants mostly on soil Funariaceae
12. Alar cells differentiated, quadrate to oblong or oval, often dark coloured, yellow to red 13
12. Alar cells undifferentiated 14
13. Alar cells dark red; low, somewhat irregular membrane formed around and external to peristome; plants on rocks associated with streams, mostly at high elevations Seligeriaceae p.p.
13. Alar cells often reddish-brown or golden; low, external membrane lacking; plants on various substrates and low to high elevations Dicranaceae p.p.
14. Leaves appearing 3-ranked; seta conspicuously elongate (to 10 cm long or more); exostome reduced, endostome well developed; plants of mid to high elevations in boggy sites Meesiaceae
14. Leaves spirally arranged, or more than 3-ranked; seta usually shorter; peristome various; plants either of drier sites or aquatic, rarely of boggy sites 15
15. Laminal cells distally linear-oblong or -fusiform and flexuous or not; capsules inclined to more often pendulous; peristome double, endostomial cilia often present, or represented by only an hyaline endostome with a low membrane Bryaceae p.p.
15. Laminal cells isodiametric to short or long rectangular; capsules mostly erect to inclined; peristome single or double (Rhizogoniaceae) 16
16. Laminal cells above base isodiametric, small, thick-walled; plants often dark green, reddish-brown or blackish 17
16. Laminal cells often short to long rectangular, or distally grading into subquadrate cells, walls thin to rather thick-walled; plant mostly light to dark green 19
17. Costa in cross-section generally well developed, stereids above and below guide cells or only below, upper and lower epidermal cells differentiated or not; capsules often long exserted; peristome teeth often divided into 32 filaments; plants on soil or rocks, dry or wet sites, at all elevations Pottiaceae p.p.
17. Costa in cross-section little or not differentiated; capsules short exserted or immersed, 4-valved or with peristome teeth perforate or divided only distally; plants confined to rocks and at very high elevations (páramo or puna) 18
18. Capsules 4-valved (peristome and operculum lacking); leaves strongly subulate from an ovate base or ovate with a very broad, diffuse costa to ca. 1/2 lamina length Andreaeaceae p.p.
18. Capsules with peristome, teeth often perforate or divided above; leaves percurrent to excurrent as a hyaline awn Grimmiaceae p.p.
19. Leaves elliptic, obovate spathulate, obtuse to rounded; peristome either with 16 teeth in 8 pairs or exostome extremely reduced 20
19. Leaves mostly ovate-lanceolate to narrowly lanceolate; margins entire to serrate; peristome with teeth when present not paired nor with exostome extremely reduced 22
20. Leaves mostly 2 mm long or more; capsules with a modified, enlarged neck, often inflated or larger/long than urn Splachnaceae p.p.
20. Leaves mostly 1.2 mm long or less; capsules lacking a modified neck 21
21. Leaves obovate to elliptic, leaf apices not apiculate; perichaetial leaves similar to stem leaves, not long sheathing; capsules smooth Splachnobryaceae
21. Leaves obovate to spathulate, leaf apices apiculate (most leaves); perichaetial leaves strongly differentiaed from stem leaves, long sheathing; capsules 8-ribbed Rhachitheciaceae p.p.
22. Capsule neck elongate, 1.5-3 times longer than urn, stomata numerous in neck region; peristome absent or single (vertically striate below); costa subpercurrent; plants of disturbed sties, rather uncommon Bruchiaceae
22. Capsule neck distinctly shorter than urn, or absent; peristome double or single (and often divided above); costa subpercurrent to excurrent; plants of various habitats 23
23. Perichaetia at mid stem or base; leaf margins bistratose and doubly toothed, if singly toothed then distal stem tips with cylindrical, papillose gemmae; plants epiphytic or terrestrial Rhizogoniaceae p.p.
23. Perichaetia terminal on stems; lacking the above combinations of characters; plants on soil or rocks 24
24. Capsules ribbed; annulus compound, exceeding or nearly so the length of the peristome; leaves setaceous from an ovate base; plants rare Seligeriaceae p.p.
24. Plants lacking the above combination of characters 25
25. Peristome teeth terete, often divided to near base, into 32 filaments Ditrichaceae p.p.
25. Peristome teeth flat below, entire or divided above Dicranaceae p.p.