" Predisposition " and " Immunity " in Plants. 



325 



from those of B. Or, to put the matter in another way, a given 

 species of host-plant x is susceptible to infection from the fungus 

 derived from a given species or variety y, but immune to the 

 same fungus derived from a species or variety z, because the cells 

 of x contain a substance, or offer conditions, favourable to the 

 fungus derived from y, but not to that derived from z. 



Table VII. 



80 



70 



60 



50 



40 



30 



20 



10 



■J 



<- 























\ 























1 



X 



fy 





































\ 









' I 



~N 







s 



y^"-' 









• 

 S 



s 







/ 





/ 



— \ 



s 



"r- 



- -" 



L_ - — 



X > 1 





\ 

 \ 

 \ 



/ x 



/ 



/ \ 



/ 













^ 

























Above = 



■I Pq 



cq 



Below = - 





Infection = x-x-x-x 



Number of stomata per 1 sq. mm. on first green leaf. 

 Vertical heights = multiples of 1 /x. The measurements of numbers of stomata 

 given are obtained by three distinct methods (see Table V.) for each surface. 



But there are yet other possibilities. The influence of its 

 former host A on the fungus may have been such — in virtue of 

 the substances afforded it in nutrition, or of conditions of other 

 kinds — that they have imparted to it properties which enable it 

 to overcome the obstructive substances or conditions offered by 

 the living cells of the prospective host B, but not such as render 



24—2 



