THE POLYTRICHACE.E OF WESTERN NORTH AMERICA 307 



thick; lamina smooth at back. Margin plane or broadly incurved, 

 not bordered, usually with large teeth. Lamellae on upper side only, 

 very numerous, erect, high, not wavy from side to side, entire or 

 nearly so. Vein often toothed at back near apex. Cells of sheath 

 without chlorophyll, elongated-rectangular to linear, toward the 

 edge longer than along the vein; cells of lamina small, thick 

 walled, quadratic or hexagonal, at base often broader than long, 

 often in rows at the margin. 



Calyptra matted with very long white to brown hairs which cover 

 the whole capsule. 



Capsule erect when young, later inclined, finally often horizon- 

 tal, 4-6 angled or terete, cubical to oblong; hypophysis hemispheric 

 and grading into capsule, or discoid and deeply constricted from 

 capsule, with large i-celled stomates. Peristome present; teeth 64. 

 Lid large, plane to conic, beaked. Pedicels single, long, rigid, yel- 

 lowish-red to purple, twisted to the right above when dry. 



Number of species in western North America, 12; total number 

 species, about 104. 



THE WEST NORTH AMERICAN SPECIES, A COMPARISON AND KEY. 



i. Leaf margin serrate to sheath or nearly so. 

 2. Margin plane or erect. 



3. Leaves sharply pointed, the point composed mostly of the ex- 

 current vein. 

 4. Leaf point red, dentate, about i mm. long. 



5. Marginal cells of lamellae like the rest, sometimes slightly 

 flattened or elongated, not thickened, width to height 

 about as i: i. 



6. Capsule about as i :i, obscurely 5-6 angled. 

 7. Plants 2^-10 cm. long. 



a. Cells near middle of sheath and distance from 

 margin to vein about 3-4 times as long as wide; 

 leaf blade about middle i cell thick for 4-8 cells 

 from margin i. P. gracile. 



6. Capsule about as i :if, sharply 4-6 angled. 

 7. Plants 7-20 cm. high.' 



a. Cells near middle of sheath and distance from 

 margin to vein about 6-10 times as long as wide; 

 leaf blade about middle i cell thick for 2-3 cells 

 from margin 2. P. attenuatum. 



5. Marginal cells of lamellae oval or flattened, thickened, width 



to height about as 1^-2 :i. 

 6. Capsule about as i : 2-2^, sharply 4-6 angled. 



7. Plants 3-6 cm. high j. P. ohioense. 



