Process of Power Changes 21 



the second plant to raise a third, we again find 

 that it starts more easily, and so on time after 

 time. By many repetitions the plant develops 

 the power of producing roots abundantly from 

 cuttings. By exercising the powers which it has 

 it acquires powers which it did not have before, 

 and which never existed in any ancestor. 



There is no selection in this matter. No seeds 

 are produced. The final plant is really a de- 

 veloped section of the original plant, but has 

 powers which the original plant did not have. A 

 large number of our greenhouse plants are now 

 produced by cuttings, but originally came from 

 stock which would grow that way only with dif- 

 ficulty. 



Henslow says that the hypocotyl of a seedling 

 sunflower, which would break under a weight of 

 160 grams, bore a weight of 250 grams after 

 being subjected for two days to a weight of 150 

 grams. After some further physical training, the 

 weight was increased to 400 grams without caus- 

 ing injury. Here we have in plants something 

 which corresponds exactly to the development of 

 muscular strength by muscular exercise in ani- 

 mals. Similar and even more pronounced results 



