No. 494] FASCIATIONS OF KNOWN CAUSATION 95 



the parasite never comes in direct contact with that of 

 the host. Yet their influence extends to cells at some 

 distance from the point of infection. Even where the 

 hyphse do not actually enter the cell, a stimulation to 

 abnormal growth often takes place. Experimentally 

 mere mechanical action has brought about profound 

 changes. Molliard was able to induce the formation of 

 double flowers through mechanical irritation. 



That the action of galls is of a chemical nature is well 

 shown by Molliard, 55 who describes and figures profound 

 nuclear changes preceding the hypertrophy of Geranium 

 sanguineum attacked by Phytoptus Geranii. 



If fasciations, which are due directly to chemical 

 changes within the cells, may be inherited, then why not 

 galls? But acorns from an oak covered by galls produce 

 normal plants only. Still, one might expect galls to be 

 inherited in preference to fasciations. Does not de 

 Vries 56 say: ''It is clear that the beautiful, highly com- 

 plex and judicious structure of the cynipid galls, with 

 their food tissue, layers of stone cells, and the tannin- 

 bearing, loose, outer parenchyma, in thickness adapted 

 to the egg apparatus of the parasites and inquilinae, can 

 not be brought about by a mere mechanical stimulus." 

 Kerner goes so far as to say that it is within the limits 

 of possibility that the first double flowers were caused by 

 some gall. 



There is no direct evidence of the inheritance of abnor- 

 malities brought about through the influence of gall in- 

 sects or their larva?. Fasciation, however, from whatever 

 cause, may be inherited by a greater or less percentage 

 of the offspring. We may then assume there must be a 

 predisposition to the formation of fasciation in all plants 

 which up to this time have been known to produce them. 

 Probably this disposition is present in all other plants. 

 The assumption of a mere excess of nutrition is not 



"Molliard, M. Hypertrophic pathologique des cellules vegetales. Rev. 

 gen. hot., 9«: 33, 1897. 



58 Mutationstheorie, 1 : 290. 



