OBTAINING VARIATIONS 111 



ency 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 per- 

 haps is of greatest interest is the fact that when 

 petals have once shown a tendency to such modi- 

 fication, this character is heritable, and the prog- 

 eny 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 on still wider variation. In other words, the 

 plant that has developed an extra petal or row 

 of petals has acquired a tendency that will urge 

 it to the production of still greater modifications 

 of the floral envelope. 



In the case of the balloon-flower, the plant 

 that had developed a second row of petals, when 

 its progeny were carefully examined, was found 

 to have transmitted the anomaly to a certain 

 number, and among the progeny of these there 

 presently appeared one that had a third row of 

 petals. So in the course of comparatively few 

 generations there had been produced a race of 

 balloon-flowers that had trebled the number of 

 petals that hitherto had been the recognized 

 complement for flowers of this race. 



