74 MendeliiiH Inkerilance and I'lilui'' Hnxt In Whral 



intermediate between the homozygous susceptible and "imuiune" 

 cultures in regard to their rusted condition, and, taking their abnormal 

 growth into consideration, one is probably correct in concluding that 

 they were the offspring of F., heterozygotes. 



(/) Nineteen cultures were grown from i\ phmts which had been 

 badly rusted in 1918. Fifteen of these proved to be homozygous sus- 

 ceptibles, every plant being either badly or very severely attacked. One 

 culture (14/2) was seriously affected by di'ought, but was 2)robabiy also 

 of the same genetic constitution for susceptibility. The three other 

 cultures, 74/12, 6/4, and 31/1, gave clear evidence of segregation. 



{(j) The 24 cultures raised from very badly rusted i\ plants all 

 proved to be homozygous snsceptibles. In each of these all the plants 

 were distinctly worse attacked than their parents had been in the pre- 

 vious season (Tabic VII). 



Table VJl. Results from 21 7'^^ vultures (1919) raised from F^ plaids 

 wkicJi were very badly rusted in 1918. Every plant in this grouj) of 

 cultures was very severely rusted in 1919. 



Percentage of plants rusted 



