POLYTRICH ACEAE 1 69 



cubical, only a little loncjer than broad; the operculum 

 is short-beaked; and the calyplra is long, wholly cover- 

 ing the capsule and extending a little below. 



Range, throughout North America, a cosmopolitan species. 



The large sterile patches of Polytrichum, with stems 

 longer than in P. pilijcrum, conspicuous on banks and 

 in open places, especially in the spring when the new 

 growth first starts, are most likely to be the var. pcri- 

 goniale. This variety is not mentioned by most moss 

 students, as both the short and tall plants are spoken 

 of as P. commune. Fruited specimens are frequently 

 found and are sometimes abundant, but they rarely 

 grow so extensively as the sterile plants. It is not un- 

 usual to fmd male plants with one year's growth start- 

 ing from the middle of the rosette, and again develop- 

 ing the male heads at the tip, then the next year's 

 growth starting in the same way. (Plate VII, Fig. la.) 

 This growth occurs in other species also. P. commune 

 and this variety are distinguished from other common 

 Polytrichums by the almost cubical capsule, with the 

 short-beaked operculum, and long calyptra and by the 

 leaves without the margins folded in, yellowish- green or 

 darker, but not the bluish-green of P. juniperinum, 

 which in some localities is a very common species grow- 

 ing extensively. Other species have a longer capsule 

 and some have a longer beak to the operculum. P. 

 piliferum often grows in large patches, but the plants 

 are much smaller in every way. 



