1. Alar cells numerous, forming a cluster or grouping in tiers, mostly colored, quadrate or rectangular, not much inflated, usually thick-walled.......................................................................................................2
1. Alar cells oval or kidney-shaped, usually translucent, inflated, thin-walled, forming at least one distinctly defined basal row................................................................................................................................7
2. Caducous flagellate branchlets present on branches; propagula absent.............................. 10. Isocladiella
2. Caducous flagellate branchlets absent; asexual propagula, if present, filiform.......................................... 3
3. Branches complanate with an enlarged and caudate terminus; leaf bases decurrent; leaf axillary propagula abundant..............................................................................................................4. Clastobryopsis
3. Branches not complanate, without an enlarged and caudate terminus; leaf bases not decurrent; leaf axillary propagula few............................................................................................................................4
4. Rhizoids numerous on stems and branches...........................................................18. Struckia
4. Rhizoids rare, not commonly persistent.....................................................................................5
5. Plants small, slender, mat forming, with irregular long branches; leaves elongate-ovate, abruptly acute; endostome segments broad, short; cilia absent.........................................................6. Gammiella
5. Plants large, stout, weft forming, with irregular short branches; leaves ovate-lanceolate, acuminate; endostome segments narrow, as long as the teeth; cilia present................................................ 6
6. Plants often growing on tree bark; paraphyllia absent; opercula obtuse; basal membrane of endostome low; cilia short........................................................................................................................ 14. Pylaisiopsis
6. Plants often growing on rotten logs; paraphyllia present; opercula shortly rostrate; basal membrane of endostome high; cilia long........................................................................................9. Heterophyllium
7. Leaf cells smooth................................................................................................................... 8
7. Leaf cells papillose or prorate.................................................................................................19
8. Stems irregularly bi- to tri-pinnately branched; stem and branch leaves different in size and shape..... 22. Wijkia
8. Plants regularly branched; stem and branch leaves similar, or different only in size................................. 9
9. Leaves abruptly constricted into a narrow or filiform acumen....................................................10
9. Leaves acute or gradually long acuminate................................................................................11
10. Leaves erect spreading, at most slightly falcate, without a broad sheathing base; calyptrae small, cucullate.........................................................................................................16. Rhaphidostichum
10. Leaves strongly falcate, with a broad sheathing base; calyptrae large, campanulate......21. Warburgiella in part
11. Peristome single........................................Meiothecium (reported from Taiwan, not seen for this study)
11. Peristome double..............................................................................................................12
12. Exostome teeth non-striate............................................................................3. Chionostomum
12. Exostome teeth striate........................................................................................................13
13. Leaves lingulate to ligulate, margins bordered, irregularly and strongly toothed in the tongue-like portion..
...............................................................................................................12. Pseudotrismegistia
13. Leaves ovate, oblong to lanceolate, margins not bordered, entire or serrulate............................14
14. Leaves often triseriate...........................................................................5. Clastobryum in part
14. Leaves conspicuously in more than 3 rows..........................................................................15
15. Alar cells few, 4–5, not forming a continuous basal row reaching to costa...............................16
15. Alar cells, including the well developed supra-alar cells, more than 6, often forming a continuous basal row reaching to costa......................................................................................................................17
16. Plants green or yellowish brown, with filiform propagula in leaf axils; leaves not concave.....................
.......................................................................................................................13. Pylaisiadelpha
16. Plants reddish or purplish brown, without filiform propagula; leaves strongly concave.... 8. Hageniella
17. Leaf apex toothed; exothecial cells not collenchymatous, thickened along vertical cell walls.... 2. Brotherella
17. Leaf apex entire or weakly toothed; exothecial cells strongly collenchymatous...............................18
18. Leaves strongly concave, margins involute; alar cells large, often curved, kidney-shaped........................
...............................................................................................................1. Acroporium in part
18. Leaves flat or slightly concave, margins plane or reflexed; alar cells small, oval to oblong.....................
................................................................................................................17. Sematophyllum
19. Leaves triseriate, leaf cells sparingly papillose or prorate............................5. Clastobryum in part
19. Leaves not triseriate, leaf cells uniformly papillose or prorate................................................20
20. Leaf cells pluripapillose or uni- or bi-seriately papillose........................................................ 21
20. Leaf cells unipapillose or prorate.........................................................................................22
21. Leaves falcate-secund; setae papillose above; opercula obliquely long-rostrate; exothecial cells strongly collenchymatous............................................................................................15. Radulina
21. Leaves not clearly falcate-secund; setae smooth throughout; opercula conic, short; exothecial cells not collenchymatous...........................................................................................19. Taxithelium
22. Leaves strongly falcate, leaf cells weakly prorate................................................ 21. Warburgiella in part
22. Leaves erect-spreading, flexuose or slightly curved, leaf cells papillose or strongly prorate.............. 23
23. Opercula conic, short; exothecial cells not collenchymatous...................................................24
23. Opercula long-rostrate; exothecial cells collenchymatous.......................................................25
24. Leaves ovate at base, long-filiform-acuminate toward apex; leaf cells shortly fusiform..........................
.................................................................................. Acanthorrhynchium (reported from Taiwan, not seen)
24. Leaves oblong-ovate or lingulate, obtuse or bluntly pointed at apex; leaf cells linear...... 7. Glossadelphus
25. Outermost alar cells long and curved; capsules erect to suberect............................1. Acroporium in part
25. Outmost alar cells not long and curved; capsules inclined or pendulous....................................26
26. Leaves hooded in the upper half; apex somewhat constricted and narrowed into an acumen; alar cells often thick-walled............................................................................................................... 11. Papillidiopsis
26. Leaves concave throughout; apex gradually attenuate; alar cells mostly thin-walled......20. Trichosteleum