D1V. II 



PHYSIOLOGY 



323 



been produced by external factors. It has already been pointed out 

 (p. 288 ff.) in what way innumerable external factors influence the form 

 of the plant. The differences that characterise the land and water 

 forms of an amphibious plant or the forms of one species growing in 



FIG. 270. Taraxacum ojficinale. 1, cultivated in the plains ; 2, in the Alps. (Both similarly reduced. 



After BONNIER.) 



the plains and on mountains are considerable. The plants represented 

 in Fig. 270 are portions of one and the same individual; 1 was 

 grown in the plain and 2 on a mountain. In order to ascertain the 

 full capacity for modification of any plant it is necessary to cultivate 

 it under all conditions under which it can exist. Such investigations 

 have been carried out with success by KLEBS. If it were possible to 



