FRUCTIFICATION. 35 



other genera have also, in addition to this, a series of fine 

 threads intermingled, which have afl^orded characters for 

 separating the tribes of this extensive genus"^. 



Covering the capsule till it has reached the necessary 

 stage of maturity, we find the opercidum, or lid, a cup- or 

 cone-shaped body, present in all the leading genera. When 

 it has performed its function it falls off', allowing the peri- 

 stome to perform its office in dispersing the spores. Aii- 

 draa, Phascum, etc., as will ■be seen in the Classification, 

 have no operculum. 



The last portion of the fruit of Mosses we have to de- 

 scribe is the calijptra, or veil. In the preliminary remarks 

 it will be remembered that when this covering membrane 

 is fixst discovered it is seen to envelope completely the ari' 

 theridia, or young fruit-stalks. As these increase in height, 

 the membrane, being divided transversely, is pushed up by 

 them, and assumes gradually the form characteristic of the 

 species. The calyptra in some genera, S/Jiagnnm, etc., is 

 very fugacious, so cannot be detected in such, unless the 

 fruit is examined in a very young state. 



* The genus Gymnostohium — Beai-dless Moss — and some of its congeners, 

 are distinguished hy being destitute of a peristome, though in many of these 

 there is an annuhir ring present, which may be of service iu the economy uf 

 the plant. 



