LUTHER BURBANK 



cause it to fruit earlier than it otherwise would do. 

 And any disturbance of equilibrium of this sort 

 may lead to anomalies in the precise character of 

 the flower. 



Possibly the reason why the petals of the flower 

 are most likely to be altered as to number, and 

 also as to color, is the fact that these are about the 

 newest of all the plant structures. We have seen 

 that the petals are not themselves essential to the 

 fertilization of the plant they are only advertise- 

 ments to attract insects. They were developed 

 late in the evolutionary history of the plant, and 

 their variability is an additional evidence of their 

 modernity. The fact that so many of our culti- 

 vated plants have become "double" is in itself suf- 

 ficient proof of the tendency of the petals to be 

 modified under conditions of change of climate 

 and nutrition to which the cultivated plant is 

 subjected. 



But from our present standpoint, what perhaps 

 is of greatest interest is the fact that when petals 

 have once shown a tendency to such modification, 

 this propensity is heritable, and the .progeny of 

 the plant will reveal some members at least that 

 show the same characteristic. 



Moreover, the "momentum of variation" to 

 which I have so frequently referred will make 

 itself felt in the tendency of these variants to take 



[28] 



