34 HISTORY OF BRITISH MOSSES. 



protection of the spores after the lid has dropped, and for 

 their subsequent dispersion when thoroughly mature. That 

 this is the purpose it is mainly intended to promote, is evi- 

 dent from its marked hygrometric properties, as it expands 

 freely when the air is dry and warm, and as surely closes 

 whenever the atmosphere is charged with moisture. The 

 simple experiment of breathing on one of those of the larger 

 species, especially if the lid has but recently fallen off, will 

 well illustrate this fact. Even to the naked eye there are 

 few portions of the structure of Mosses, or indeed of any 

 other cryptogamic plants, that are more worthy our notice 

 and admiration ; but it is when examined by a low micro- 

 scopic power that its beautiful structure is fully disclosed. 

 The number of divisions or segments of which it consists 

 is very regular, and thus useful characters for distinguishing 

 genera have been di-awn from it. The segments are four, 

 or multiphcates of that number — S, 16, 32, and 64, none 

 being intermediate. While pale yellow is the leading colour 

 of the peristome, we find some variety in this respect, some 

 beinci; almost black and others brilliant crimson. In some 

 genera we find a double peristome, the inner one being of 

 a more dehcate texture and paler in colour, arising from 

 the inner membrane of the capsule. Some Hi/pnums and 



