176 Retrograde Varieties 



strict methods of criticism very few instances 

 will be found that satisfy legitimate demands. 

 On this ground it is by far safer in the present 

 state of our knowledge, to accept bud-variations 

 only as direct proofs of true atavism. And 

 even these may not always be relied on, as some 

 hybrids are liable to split up in a vegetative 

 way, and in doing so to give rise to bud-varia- 

 tions that are in many respects apparently sim- 

 ilar to cases of atavism. But fortunately such 

 instances are as yet very rare. 



After this discussion it would be bold indeed 

 to give instances of seed-atavism, and I believe 

 that it will be better to refrain wholly from do- 

 ing so. 



Many instances of so-called atavism are of 

 purely morphologic nature. The most interest- 

 ing cases are those furnished by the forms 

 which some plants bear only while young, and 

 which evidently connect them with allied species, 

 in which the same features may be seen in the 

 adult state. Some species of the genus Acacia 

 bear bipinnate leaves, while others have no 

 leaves at all, but bear broadened and flattened 

 petioles instead. The second type is presumed 

 to be descended from the first by the loss 

 of the leaflets and the modification of the stalks 

 into flat and simple phyllodes. But many of 

 them are liable to recall this primitive form 



