“ 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 
Table VII. 
Above = 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 
maximus 
