S. F. Armstrong 



77 



In considering the F^ results it was seen tiiat the 1 : "2 : 1 ratio was 

 not very closely approached, though the figures strongly suggested its 

 existence. The numbei' of iiist-free and badly rusted plants were, taken 

 together, consideraldy less than those placed in the intermediate grou]). 

 The jDrobable explanation is that this deviation arises partly from the 

 difficulty in determining the exact extent of attack by inspection only, 

 and partly from the existence of other factors which are capable of 

 modifying the degree of attack. 



Table VII 1. SuDimari/ of resvltf fnihi 170 Fg rulfiires in 1919. 



Condition of the F^ cultures, 1919 

 Extent of rust Numlier of , ' 



attack on the F., F^ cultures All plants C'rtntained susceptible All plants 



])arents in 1918 raised, 1919 susceptible and resistant plants rust resistant 



Very bad 24 -u — — 



Bad 19 1() 3 — 



Moderate (!.•? 14 49 — 



SU^ht :!5 — 33 2 



Traces 12 — 9 3 



None 17 — 2 15 



Totals 



170 



54 



96 



20 



Table IX. Ajiproximale genetic consiitutimi of the Fo f/eneration [avtumn- 

 sown portion) as regards susceptibility to Yellow Rust. These figures 

 are arrived at hg the direct application of the F^ results. 



