Retrograde Varieties 137 



wards, and their lower surfaces downwards, and 

 all of them are by this means placed in a single 

 horizontal plane, and branching takes place in 

 the same plane. Evidently this general ar- 

 rangement is another response to gravity, and 

 it is the failure of this reaction which induces 

 the branches to grow upwards and to behave 

 like stems. 



Both weeping and fastigiate characters are 

 therefore to be regarded as steps in a negative 

 direction, and it is highly important that even 

 such marked departures occur without transi- 

 tions or intermediate forms. If these should 

 occur, though ever so rarely, they would proba- 

 bly have been brought to notice, on account of 

 the great prospect the nimierous instances 

 would offer. The fact that they are lacking, 

 proves that the steps, though apparently great, 

 are in reality to be considered as covering single 

 units, that cannot be divided into smaller parts. 

 Unfortunately we are still in the dark as to the 

 question of the inheritance of these forms, 

 since in most cases it is difficult to obtain pure 

 seed. 



We now consider the cases of the loss of su- 

 perficial organs, of which the nectarines are 

 example. These are smooth peaches, lacking 

 the soft hairy down, that is a marked pecul- 

 iarity of the true peaches. They occur in differ- 



