268 DISEASE IN PLANTS. 



Hut the case is not hypothetically impossible, 

 although the distant relationships of the two 

 groups of organisms render it extremely im- 

 probable among the higher plants. It is by no 

 means so improbable, however, that further research 

 may show cases where the egg-cell of a lower 

 cryptogam e.g. another fungus may be affected 

 either directly, or indirectly, by the protoplasm 

 of a parasitic or symbiotic hypha, as suggested 

 by the extraordinary phenomena of symbiosis. 



Some of the variations in grafted plants are found 

 to predispose the plant to disease, or the reverse, 

 and cases may be cited where the resulting shoots, 

 foliage, or fruits, or seedlings more readily fall 

 a prey to, or resist, parasitic fungi and insects 

 than the ungrafted plants. Daniel gives instances 

 of such ^.^. among other examples, Peas grafted 

 on Beans yield seeds which suffer more from 

 Erysipheae than the normal seedlings. But the 

 best known cases are those of Vines in their 

 relations to Phylloxera, already referred to 



(p. 15 5). i 



Several instances are also known where grafted 



plants show more or less resistance to such factors 

 of the environment as low temperatures ; grafted 

 or budded Roses often suffer much from Erysipheae, 

 and so forth. Much research is still needed to 

 determine how far these matters depend on real 

 alterations in the nature of the graft, or are only 

 true for the localities in which the experiments have 

 been made, a point which has, I think, been over- 

 looked by all observers. 



