MOSSES 81 



right over the edge of the capsule mouth. This 

 is a sight that may often he seen, by scrutinising 

 the green tufts nestling in the crevices of the 

 hark of such a tree as the sweet chestnut or the 

 wych elm, with a good magnifying-glass. 



We are naturally led to ask the why and the 

 wherefore of facts such as these; for when we 

 find them happening with never-failing regularity, 

 we may he pretty sure that there is some very 

 practical reason for their occurrence. Sir Edward 

 Fry, in his delightful book entitled "British 

 Mosses," suggests that the possible explanation 

 may be that, whereas in many mosses the spores 

 germinate best under the influence of moist 

 surroundings (and here the peristome opens in 

 wet weather and closes in dry), in other cases 

 dry conditions are most favourable to their 

 development (and here the peristome teeth only 

 stand erect when the atmosphere is free from 

 moisture). If this suggested explanation of some- 

 what remarkable facts is the correct one, it 

 certainly affords a very marvellous instance of 

 adaptation to surrounding circumstances, brought 

 about, one must presume, by the operation of the 

 principle of natural selection. 



Summary of Life-history. Before proceeding to 

 speak of the more special modes of reproduction 

 that we meet with, I propose, with the help of 

 Plate I., to focus the contents of the foregoing 

 pages, by shortly summing up the various steps 



6 



