308 FRYE 



5. Marginal cells of lamellae notched in cross section. 

 6. Capsule about as mJ-i-J, sharply 4-angled. 



7. Plants 5-45 cm. high 5. P. commune. 



4. Leaf point red, smooth, mm. or shorter. 



5. Marginal cells of lamellae oval or flattened in cross section, 



not thickened, width to height about as 2: i. 

 6. Capsule unknown. 

 7. Plants 4-8 cm. high 4. P. inconstans. 



i. Leaf margin serrate from the middle up. 



2. Margin plane below, erect or somewhat incurved above. 

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



rent vein. 



4. Leaf point red, dentate, i mm. long or shorter. 

 5. Marginal cells of lamellae notched in cross section. 

 6. Capsule unknown. 



7. Plant 4-8 cm. high 6. P. jensenii. 



i. Leaf margin entire. 

 2. Margin plane or erect. 



3. Leaves sharply pointed, the vein excurrent as an arista. 

 4. Arista red, smooth, i mm. long or shorter. 



5. Marginal cells of lamellae notched in cross section. 

 6. Capsule unknown. 



7. Plants 5-8 cm. high 7. P. yukonense. 



2. Margin plainly incurved. 

 3. Leaves blunt, cucullate. 

 4. Arista or sharp point none. 



5. Marginal cells of lamellae ovate, thickened, width to height 



about as i 12. 

 6. Capsule about as i : ij, bluntly 6- angled. 



7. Plants 2.5-10 cm. high 8. P. sexangulare. 



3. Leaves sharply pointed, the vein excurrent as an arista. 



4. Arista red, rarely somewhat colorless at tip, rough, ^-ij mm. 



long. 



5. Marginal cells of lamellae ovate or flask-shaped. 

 6. Capsule as i : ij-ij, sharply 4- angled, 3-5 mm. long. 

 7. Plants 2-10 cm. high. 



b. Stem without^ dense covering of rhizoids. 



9. P. juniperinum. 



6. Capsule about as i nj, sharply 4-angled, 2-3mm. long. 

 7. Stems mostly with dense covering of rhizoids. 



10. P. strictum. 



