THE METHOD OF DARWTN. 



he was in possession of the cause (natural selec- 

 tion), and the specialized effects and the belief 

 that these are the results of the action of natural 

 selection upon variations ; Hofmeister furnished 

 the material which natural selection could de- 

 velop, by the observation that all young plants 

 are slightly sensitive to disturbance. 



Now what was the logical setting for Darwin's 

 prediction that the capacity of revolving would 

 be found inherent, though undeveloped in almost 

 every plant in the vegetable kingdom ? If there 

 were no evidence to the contrary, it would be 

 supposed that he had been able to make the 

 prediction from the knowledge that climbing 

 plants occur throughout the plant kingdom, 

 and that therefore the source of the variation 

 must be a general tendency in plants. Such an 

 inference seems easy enough to make, as has 

 been shown in other cases, after it has been 

 made. In this case Darwin had the help of an 

 analogy upon which he could depend with con- 

 fidence. Hofmeister had furnished, by obser- 

 vation, a general source of the sensitiveness of 

 climbing plants in the slight sensitiveness of 

 young leaves and shoots in general. Sensitive- 

 ness to touch and power of circumnutation are 

 inseparable in climbing plants; what was more 

 natural, therefore, than the inference that the 



