The Causes of Individual Differences 29 



however, a cause of variation. The change is beneficial 

 because it fits together characters and environments that 

 are not in equilibrium with each other. A plant grown 

 for several years in one set of conditions becomes fitted 

 to them, so to speak, and it is in a state of comparative 

 rest. When the plant or its progeny is taken to other 

 conditions, all the adjustments are broken up, and in 

 the refitting to the new circumstances new or strange 

 characters are likely to appear. We shall leave this sub- 

 ject for the present, expecting to give it a fuller treatment 

 in a later chapter. 



Bud-variation. Bud-variation, or sport, is a name 

 given to those branches which are so much unlike the 

 normal plant in any particular that they attract atten- 

 tion. Many garden varieties are simply multiplications 

 of such abnormal branches. This bud-variation is com- 

 monly held to be such an unusual and inexplicable phenom- 

 enon that it is considered apart from all the general 

 discussions of variation. It is not, of course, a cause of 

 variability, but only an effect of some antecedent, the 

 same as seed-variation is. We have already seen that all 

 the different branches, or even nodes of any plant are, 

 in a very important sense, distinct individuals, since 

 every one develops its own organs, each is capable of 

 reproducing itself independently, and each is unlike every 

 other because it is acted upon differently by environment 

 and food supply. It is not strange, therefore, that some 

 of these individuals should now and then depart very 

 widely from the ordinary type, and thereby attract the 

 attention of the gardener, who would forthwith make 

 cuttings or set grafts from the part. Every branch is a 



