12 American Midland Naturalist Monograph No. 6 



19. Leaf-cells smooth 20 



20. Peristome of 16 broad solid teeth, sometimes somewhat bifid at the apex, 



smooth and strongly hygroscopic Seligeria, p. 53 



20. Peristome of 16 narrow, prolonged, more or less two-parted, minutely 



striate or papillose teeth 21 



21. Capsule cemuus, with a long and inflated neck; teeth cleft or perforate 



Trematodon, p. 47 



21. Capsule erect or inclined; neck short or* none; teeth cleft to the middle into 



two (or three) filiform divisions; leaves not crisped when dry 



DicraneV.a, p. 54 



21. Capsule erect to horizontal; neck none; teeth cleft about half way; leaves 



crisped when dry Oncophorus, p. 58 



22. Monoicous; leaves tufted; capsules strumose, costa with distinctly hetero- 

 geneous tissues Oncophorus, p. 58 



11. Dioicous; leaves flexuose-spreading or secund; capsule more or less distinct- 

 ly strumose 23 



23. Basal auricles of leaves large and inflated; seta cygneous; peristome teeth 



divided % to base Dicranodontium, p. 64 



23. Basal auricles of leaves small or none; seta not cygneous; peristome teeth 



divided about half way Dicranum, p. 59 



24. Peristome distinctly twisted; teeth 32 25 



24. Peristome not distinctly twisted; teeth 16 but often deeply^ cleft 27 



25. Leaves large, oblong to sub-spatulate; costa with two median guides 



Tortula, p. 91 



25. Leaves small and narrow, linear-lanceolate; costa with from 4-8 median 



guides 26 



26. Leaf-margins plane, not revolute; cells papillose Tortella, p. 83 



26. Leaf-margins revolute, at least below; cells smooth or papillose 



Barhula, p. 85 



27. Dark green to brownish or blackish mosses on rocks or sometimes trees; jseri- 



stome single or none 28 



27. Green plants, not blackish nor very dark 30 



28. Calyptra campanulate, plicate, covering most of urn 



OrthotTtchum, p. 103 



28. Calyptra covering about half of the capsule, split and plicate; sfxsres large 



Ptychomitrium, p. 95 



28. Calyptra large cucullate; spores very large; teech wide, truncate; annulus 



none Drummondia, p. 103 



28. Calyptra short, not plicate; annulus usually present; spores medium size to 



small 29 



29. Teeth sub-entire, cribrose or irregular cleft in upjser half Grimtma, p. 95 



29. Teeth cleft to near the base into filiform segments Rhacomitrium, p. 98 



30. Calyptra mitrate, not folded nor torn, completely covering the capsule; 



capsule erect; leaves ligulate to spatulate Encalypta, p. 93 



30 Calyptra cucullate 31 



31. Teeth merging below into a more or less continuous basal wall or membrane .. 32 



31. Teeth not merging below into a continuous membrane 35 



32. Upper leaf-cells papillose; costa with one or two rows o^ larger cells ven- 

 tral to the 2-4 median guides Desmatodon, p. 90 



32. Upper leaf-cells papillose; costa with 4-6 median guide cells and a well 



develofjed stereid region on ventral side Didymodon, p. 84 



32. Leaves mostly smooth; peristome-teeth mostly medium length to long 33 



33. Capsule inclined, distinctly plicate when dry; leaf-cells roundish-quadrate above 



Ceratodon, p. 52 



33. Capsule erect, nearly or entirely smooth when dry; leaf-cells elongated (2:1 or 



more) above 34 



34. Leaves glaucous (Saelania) 



