96 THE SURVIVAL OF THE UNLIKE. [ill. 



gressive variability in the vegetable kingdom with seeds 

 or the results of sexual union. 



Whilst it is not my purpose to discuss the original 

 sources or causes of bud -variations, I cannot forbear to 

 touch upon one very remarkable fact concerning rever- 

 sions. It is a common notion that all bud -varieties are 

 atavistic, but this position is untenable if one accepts the 

 hypothesis, which I have here outlined, of the ontoge- 

 netic individuality of the phyton, and if he holds, at the 

 same time, to the transforming influence of environment. 

 It is also held by some that bud -varieties are the effects 

 of previous crossing, but this is controverted by Darwin 

 in the statement that characters which do not pertain 

 to any known living or extinct species sometimes appear 

 in bud -varieties ; and the observations which I am 

 about to recite also indicate the improbability of such in - 

 fluence in a large class of cases. The instances to which 

 I call your attention are, I think, true reversions to 

 ancestral types. Those of you who have observed the 

 young non- blooming shoots of tulip -tree, sassafras and 

 some other trees will have noticed that the leaves upon 

 them often assume unusual shapes. Thus the leaves of 

 sassafras often vary from the typical oval form to three - 

 lobed and mitten -shaped upon the strong shoots. There 

 are the most various forms on many tulip -trees, the leaves 

 ranging from almost circular and merely emarginate to 

 long- ovate and variously lobed; all of them have been 

 most admirably illustrated and discussed recently by 

 Holm in the preceedings of the National Museum. Holm 

 considers the various forms of these liriodendron leaves 

 to be so many proofs of the invalidity of the fossil spe- 

 cies which very closely resemble them. This may be 

 true, for there are probably no specific names of organ- 



