Jennings: Manual of Mosses — 31. Hypnaceae 217 



6. Hygroamblystegium 



G. Not as above; paraphyllia none or scarce H 



H. Leaf-cells linear-vermicular to the leaf-base, mostly with blunt ends, alar cells 

 forming a small, distmct, fairly well-defined group of quadrate or rectangular 



cells 1 1. Hygrohypnum 



H. Leaf-cells hexagonal and 2-6 times as long as wide or prolonged-linear and be- 

 coming wider and shorter basally, alar cells, forming a group which is large 



and often extends to the costa -.I 



I. Ends of shoots usually circinate. Leaves falcate to circinate; alar cells parenchyma- 

 tous; mostly enlarged and mflated 8. Drepanocladus 



I. Alar cells more or less prosenchymatous or rounded J 



J. Median leaf-cells prolonged-linear; leaves concave, large, ovate to oblong or cir- 

 cular 9. Calliergori 



J. Median leaf-cells prosenchymatous-hexagonal, 2-6 times as long as wide; aquatic; 



leaves mostly erect-spreading 6. Hygroamblystegium 



K. Leaves cordate to ovate-lanceolate, acuminate; costa weak; reaching the middle of 

 leaf or beyond; leaf-cells rarely linear, mostly parenchymatous and 4-sided or 



prosenchymatous and 6-sided; small plants; capsules relatively large 



1. Amblyslegium 



K. Characters not combined as above L 



L. Leaf-cells narrowly hnear; leaves broadly ovate or cordate, with reflexed-squar- 



rose and subulate-acuminate tips 12. Campylium 



L. Leaf-cells and leaves not as above M 



M. Small plants; leaves ovate to oblong-lanceolate, long-acuminate, 0.7-1.0 mm long; 



cells narrowly prosenchymatous; plants shining 3. Homomjllium 



M. Not as above N 



N. Slender, dull; leaves spreading, lanceolate to lance-linear; median leaf-cells rhom- 

 boidal to oblong-hexagonal, 2-4 or rarely 4-8 times as long as broad; oper- 

 culum not rostrate 2. Amblystegiella 



N. Median leaf-cells prolonged-linear, mostly very narrow O 



o. Leaves erect-spreading to imbricated, oblong-ovate to rounded, obtuse or apiculate, 

 often deeply concave and cucullate; costa short and double or none; no para- 

 phyllia 10. Calliergonella 



O. Leaves more or less falcate-secund to circinate, from a mostly narrowed and some- 

 what decurrent base becoming ovate- to triangular- or cordate-lanceolate, more or 

 less slenderly acuminate, costa weak, reaching somewhat above the leaf-middle or 



even in some cases excurrent; no paraphyllia 8. Drepanocladus 



O. Not as above P 



P. Paraphyllia numerous; leaves more or less erect, spreading to squarrose-recurved, 



from abruptly to shortly acuminate, mostly plicate, concave 16. Hylocomium 



P. Characters not combined as above Qi 



Q. Leaves falcate-secund or circinate R 



Q. Stem-leaves not secund, imbricate, broadly ovate or rounded and with an obtuse 



apex; apex finely crenulate; annulus none; cilia three 17. Hypnutn 



R. Very robust; stem-leaves turgidly imbricate but strongly rugose and falcate- 

 secund, lustrous, narrowly lance-acuminate from a broadly oblong base 



15. Rhytidium 



R. Not as above S 



S. Plants distantly and irregularly pinnate; leaves squarrose or spreading and secund; 



alar cells little or not at all differentiated 14. Rhytidiadelphus 



S. Closely pinnate; leaves circinate secund; alar cells quadrate to rectangular and nu- 

 merous but not inflated 13. Ctenidium 



T. Aquatic or subaquatic on stones and rocks in running water; leaves mostly oblong- 

 ovate, flaccid, obtuse, rounded, often somewhat secund Il< Hygrohypnum 



T. Not as above V 



u. Leaf-cells very narrowly prosenchymatous, alar cells mostly not differentiated; 



