324 Professor Marshall Ward , On the Question of 
refined and subtle nature which determines such fundamental 
properties as specific relationship, variation, heredity and other 
biological phenomena. 
Table VI. 
Above = Below = - - - - Infection = x-x-x-x 
Size of stomata (extremes and commonest sizes). First green leaf. 
The vertical heights are in multiples of 1 p. The measurements of stomata 
are extremes and commonest lengths for both upper and lower surfaces. 
We are, in fact, driven to assumptions such as that the spores 
of the fungus derived from a given species A of the host-plant are 
able to attack the species or variety J5, but are unable to success- 
fully infect the species or variety C, because some resisting sub- 
stance or condition exists in the living cells of G which is absent 
maximus 
