274 FRYE 



KEY TO THE WEST NORTH AMERICAN GENERA. 



i. Lamellae on upper side of leaf 18 or fewer 2. 



1. Lamellae on upper side of leaf 20 or more 8. 



2. Leaves bordered Catharinea, p. 275 



2. Leaves not bordered 3. 



3. Leaf margin with long hairs where sheath grades into blade; 



lamina of two layers of cells; peristome wanting. 



Bartramiopsis, p. 289 



3 . Leaf margin without hairs ; lamina of i layer of cells ; peristome 



present 4. 



4. Capsule distinctly cernuous Psilopilum, p. 288 



4. Capsule straight or very nearly so Oligotrichum, p. 281 



4. Capsule wanting (for sterile specimens) 5. 



5. Lamellae straight; plant much crisped when dry. 



Oligotrichum parallelum, p. 282 



5. Lamellae wavy from side to side ; plants not or very little crisped 



when dry 6. 



6. Lamellae on back conspicuous, about equal in number and size 



to those on the upper side; leaf margin plane or erect. 



Oligotrichum aligerum, p. 284 



6. Lamellae on back inconspicuous or none ; leaf margin incurved. 7. 



7. Leaf margin abruptly incurved above the sheath; lamellae on 



back inconspicuous or none. .Oligotrichum incur vum, p. 285 



7. Leaf margin gradually incurved from base; lamellae on back 



wanting Psilopilum, p. 298 



8. Capsules 4-6 angled; teeth 64; calyptra densely hairy. 



Polytrichum, p. 304 



8. Capsules 2-4 angled ; two of the angles nearer together than the 

 others; teeth 64, calyptra with few hairs. 



Polytrichadelphus, p. 291 

 8. Capsules terete ; teeth 3 2 , or 64 in Pogonatum alpinum; calyptra 



densely hairy Pogonatum, p. 294 



8. Capsules wanting (for sterile specimens) 9. 



9. Leaf margin entire, inflexed over the lamellae in most species. 



Polytrichum, p. 304 



9. Leaf margin serrate 10. 



10. Leaves very much crisped when dry. 



Pogonatum contortum, p. 295 



10. Leaves little or not at all crisped when dry n. 



11. Marginal cells of lamellae smooth or merely grooved. 



Polytrichum, p. 304 

 ii. Marginal cells of lamellae rough or papillose 12. 



