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CHAPTER V. 



VARIATIONS OP MOSSES. 



Sexuality seems to be a necessary cause of variations. So 

 long as plants are propagated by buds, or stolons, or gems, or 

 by any other adventitious organ, there is some security for the 

 produce being similar to the parent, though modifications even 

 in these cases may be induced by varied climatic conditions, 

 or other circumstances which may exercise a certain influence 

 on the new plant. When we consider what wonderful modi- 

 fications are effected in the evolution of the embryo in the 

 animal world by mere change of position or a partial privation 

 of atmospheric air during the development of the ovum, we 

 may well be prepared for many curious phenomena amongst 

 vegetables, whose germs may be placed under anomalous con- 

 ditions. And if it is true that variations will take place when 

 increase is due only to adventitious organs, what an immense 

 source of change exists in growth by impregnation, where 

 through countless ages cross-impregnation has taken place, 

 spreading far and wide the peculiarities of individuals, in some 

 modified form, if not in all their intensity, amongst succeed- 

 ing generations. 



If the limits of species are often doubtful among Phseno- 

 gams, they are no less so amongst Cryptogams ; and Mosses 



