442 Ever-sporting Varieties 



planting part of the original earth with tlie 

 transplanted half of the plant. From this he 

 concluded that the observed changes were due 

 to the inequality of the climate. This involved 

 three main factors, light, moisture and tem- 

 perature. On the mountains the light is more 

 intense, the air drier and cooler. Control-ex- 

 periments were made on the mountains, de- 

 priving the plants of part of the light. In va- 

 rious ways they were more or less shaded, and 

 as a rule responded to this treatment in the 

 same way as to transplantation to the plain 

 below. Bonnier concluded that, though more 

 than one factor takes part in inciting the 

 morphologic changes, light is to be consid- 

 ered as the chief agency. The response is to 

 be considered as a useful one, as the whole 

 structure of the alpine varieties is fitted to pro- 

 duce a large amount of organic material in a 

 short time, which enables the plants to thrive 

 during the short summers and long winters of 

 their elevated stations. 



In connection with these studies on the in- 

 fluences of alpine climates. Bonnier has inves- 

 tigated the internal structure of arctic plants, 

 and made a series of experiments on growth 

 in continuous electric light. The arctic climate 

 is cold, but wet, and the structure of the leaves 

 is correspondingly loose, though the plants be- 



