266 DISEASE IN PLANTS. 



difficulty, or with poisonous effects, and finally 

 cannot infect the plant at all. 



Less obviously, but nevertheless existing, are 

 gradations in grafting to be observed, where one 

 and the same stock may be successfully combined 

 with a scion which improves it or which is 

 improved by it or the scion may unite but acts 

 injuriously on it, or, finally, cannot be induced to 

 unite. 



But we may go further than this in these 

 comparisons. Just as the results of pollination 

 frequently induce far-reaching effects on distant 

 tissues e.g. the swelling of Orchid ovaries, and 

 rapid fading of the floral organs so also the 

 effects of hyphae in the tissues may induce 

 hypertrophies, deflection of nutrient materials, and 

 the atrophy of distant parts ^.^. the curious 

 phenomena observed in Euphorbia attacked by 

 Uromyces and some of the distant actions in 

 grafts may be compared similarly. 



Going still further, we may compare the 

 effects of cross-breeding or of hybridisation, 

 where the progeny show that changes have 

 resulted from the mutual interactions and re- 

 actions of the commingled protoplasm, with 

 Daniel's results, in which he obtains proof of 

 such interactions of the commingled protoplasmic 

 cell-contents of grafts in the seedling progeny ; 

 although there is no probability we may even 

 say possibility in this latter case that the effects 

 are due to nuclear fusions, but only that the 

 germ-plasm of the seed-bearing plant has been 



