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NATURE-STUDY REVIEW 



(11:5— May, 1915 



capsule at maturity. The mosses of this group all grow upon the 

 ground, have strong wiry stems and a dark green color except at the 

 young and growing tips. Examined with the lens or the micro- 

 scope the peristome is found to be composed of a row of 3 2 or 64 



Fig. 



P. commune Xl- 



very short teeth attached by their tips to a membrane, the epi- 

 phragm, which resembles a tiny drumhead stretched across the 

 mouth of the capsule. The leaves are long and narrow as a rule, 

 sheathing at the base in the species we shall discuss, with a very 

 broad strong costa, which bears on its upper surface thin plates of 

 cells set edgewise to the surface of the leaf (technically called 



