168 



by hyperplasia of the whole mesophyl. On the border 

 between this complex and the normal tissue some cells of 

 the spongy parenchyma had become greatly enlarged, their 

 chloroplasts having become disorganised. After another 

 month it was noticed that the leaf-tips in the neighbour- 

 hood of the wounded spots assumed a somewhat yellow 

 colour, which gradually became more and more distinct. 

 Microscopically it could be stated that where externally 

 this yellow discoloration was vesible, the tissue round the 

 wounded spots had undergone precisely the same changes 

 as take place round the yellow visicles, caused by the 

 scale-insects, namely a gênerai hypertrophy of the cells of 

 the spongy parenchyma, while hère and there even a par- 

 tition wall had already been formed in the enlarged cells. 



As was stated above, this resuit was obtained in ail 

 cases, also in those in which small wounds had been 

 made without anything else. From which we may con- 

 clude that the leaf of Gnetitm Gnemon may be stimulated 

 to the formation of intumescences and hence of adventi- 

 tious buds by wounding, provided this is very light and 

 that consequently the process must be regarded as a reac- 

 tion on a wound stimulus. 



In a disease of carnations which also consists in the 

 formation of a sort of intumescences ') and for which it 

 has been shown by Wo o d s ") that it is caused by the 

 sting of aphides, among others, Woods thinks thegrowth 

 of the yellow, thickened spots must be ascribed to the diffu- 

 sion of an irritant, injected by the insect =*). 



That a similar hypothesis is superfluous for the „stig- 

 monose" of Gnetum Gnemon, appears clearly enough from 



1) H. V. S c h r e n k. 1. c. pag. 39. 



2) A. F. Woods, Stigmonose: a disease of carnations and other 

 pinks. (Bull. no. 19. U. S. Dept. Agr. Div. Veg. Phys. and Path. 1900). 



3) 1. c. pag. 24. 



