Evolution of Galls. xxxv 



packed palisade cells ; the lower surface is consequently 

 the situation most in favour. 



Whatever form the gall takes, the potentialities of 

 the tissue-growth exhibited by it, must be present at 

 the spot pricked by the fly. It is not necessary to 

 assume, with De Vries, that every vegetable cell contains 

 the potentialities of every other cell in a latent condition. 

 The conical growing point in every bud contains the 

 germ-plasm of the next shoot, and consequently of the 

 whole plant. 



The potentialities of growth being present, they are 

 called into activity by the larva, a result advantageous 

 to the larva and sometimes described as disinterested 

 and self-sacrificing on the part of the plant '. We 

 have just seen that, so far as the larva is concerned, 

 the peculiar structures of the gall owe their origin 

 to their success in feeding and defending it ; and so far 

 as the plant is concerned, these structures have been 

 evolved in consequence of their value in enabling the 

 plant to repair injuries in general, and the injuries 

 inflicted by larvae in particular. If John Doe raises 

 a cane to strike Richard Roe, and Richard throws 

 up his arms intuitively to parry the stroke, the action 

 does not indicate a prophetic arrangement of molecules 

 to frustrate John in particular, but an inherited action 

 of defence. The first act of an injured plant is to 



^ St. George Mivart, Nature, Nov. 14, 1889. ' Now surely it is too 

 much to ask us to believe that the germ-plasm of the plant, in the 

 first instance, before even, say, a single cynips had visited it, had in 

 the complex collocation of its molecules, an arrangement such as 

 w^ould compel the plant which was to grow from it, to grow those 

 cells and form a gall.' And in a note he adds : ' It would be very 

 interesting to know how natural selection could have caused this 

 plant to perform actions which, if not self-sacrificing (and there must 

 be some expenditure of energy , are at least so disinterested,' 



C 2 



