218 American Midland Naturalist Monograph No. 6 



leaves oblong to linear, short-pointed, ovate to linear-lanceolate, acute to long- 

 acuminate or piliferous, not decurrent 20. Isopterygium 



U. Leaf-cells often wider, alar cells broader proportionally, hyaline and thin-walled; 

 leaves broadly lanceolate to oval, more or less long-acuminate, distinctly decur- 

 rent 21. Plagiothecium 



V. Terrestrial or sub-aquatic; leaves mostly squarrose or recurved-squarrose, ovate to 



lanceolate, acuminate, decurrent; capsule curved 12. Campylium 



V. Not as above w 



w. Capsule erect and symmetric or nearly so X 



w. Capsule more or less cernuous or horizontal, and unsymmetric bb 



X. Leaves closely imbricate when dry, concave 22. Pterygynandrum 



X. Leaves erect-spreading or but slightly secund Y 



X. Leaves falcate-secund or circinate aa 



Y. Alar cells quadrate not inflated Z 



Y. Some alar cells inflated and enlarged 19. Stereodon 



2. Median leaf-cells about 2-4:1; leaves lanceolate to lance-subulate ....2. Amblystegiclla 



Z. Median leaf-cells about 6-9:1, leaves ovate to lance-oblong 5. Platygyrium 



AA. Segments attached to a wide basal membrane; cilia rudimentary or none; branches 



short, erect or ascending 4. Pylaisia 



AA. Not as above 19. Stereodon 



BB. Stem-leaves decurrent, plicate, cordate-auriculate at base and abruptly long and 



slender acuminate; quadrate alar cells numerous, none inflated 13. Ctenid'tum 



BB. Not as above cc 



CC. Robust to slender, simple or pinnate, mostly irregularly pinnate; leaves ovate- to 

 cordate-lanceolate, shortly to slenderly acuminate, generally circinate secund in 2 



series; capsule erect to symmetric to cernuous and unsymmetric 19. Stereodon 



CC. Not as above DD 



DD. Slender; lustrous; leaves ovate to lance-oblong, 0.7-1.0 mm long 



3. Homomallium 



DD. Robust plants EE 



EE. Branching plumosely complanate-pinnate; median leaf-cells about 10-15:1 ....18. Ptilium 

 EE. Branching irregularly- to bi- or tri-pinnate; stiff; median leaf-cells not more than 

 10:1 16. Hylocomium 



1. Amblystegium Bryologia Europaea* 



Autoicous: usually more or less slender, in thin and spreading mats: 

 stem creeping to ascending or even erect, irregularly to pinnately branched, the 

 branches mostly more or less erect; stem-leaves similar to branch-leaves, erect- 

 spreading to squarrose, mostly shortly decurrent, cordate- to ovate-lanceolate, 

 long-acuminate, rather concave, non-plicate, entire to serrate; costa thin, simple, 

 reaching to the middle of the leaf or beyond, rarely complete; cells paren- 

 chymatous; and rectangular to elongate-prosenchymatous and hexagonal, rare- 

 ly linear, smooth, the alar quadrate to rectangular; the inner perichaetial 

 leaves erect, broadly lanceolate, mostly costate: seta long, thin, reddish to cas- 

 taneous, flattened when dry; capsule, from an erect collum, curved to oblong 

 or cylindric, smooth when dry, constricted below the expanded mouth, annu- 

 late; peristome-teeth basally confluent, yellow to orange, lance-subulate, bor- 

 dered, dorsally cross-striate, above pale and papillose, densely trabeculate 



* Species with thinner-walled and longer leaf-cells; with costa single and well devel- 

 oped; and leaves spreading to erect-spreading are treated under the genus Leptodictyiim in 

 Grout's Moss Flora. 



