Mosses and Lichens 



The spores small and smooth. 



There are ninety-nine species in all, about fifteen of them 

 known in North America. 



Genus POLYTRICHUM 



KEY TO SPECIES 



I. Leaves entire, margins inflexed, 

 apex obtuse, P. sexangulare. 



Apex rough-awned. 



Awn coloured brown or red, 

 short. Leaves spreading 

 when moist, somewhat re- 

 curved . . P. funiperinum. 



Awn whitish, transparent, 



long P. piliferum. 



II. Leaves serrate. 



Marginal cells of lamellae not 

 enlarged in section, higher 

 than broad. 



Spore-case egg-shaped, ob- 

 scurely angled. 



Lid beaked P. gracile. 



Spore-case oblong, 4- to 6- 

 angled. 



Lid acutely conic, P. formosum. 



Marginal cells of lamellae en- 

 larged, broader than high, 

 2 to i P. Ohiense. 



Marginal cells of lamellae semi- 

 lunar, with two prominent 

 horns at corners, P. commune. 



P. in nipsrinum. 

 Leaf. 



P. piliferum. 

 Leaf. 



P. Ohiense. 



Vertical rows of cells from lamella. 

 (a) Terminal cell broader than 

 high; (6) terminal cell semilunar. 



250 



P. gracile. 

 Spore-case. 



