PARKER'S EXPERIMENTS 153 



by mild epidemics of fungoid disease it was very 

 evident that if anything could be done to prevent, 

 or even to mitigate them, then in the aggregate 

 the results would prove of great value. Experi- 

 ments were therefore started with the object of 

 testing the possibility of breeding rust-resisting 

 varieties of wheat. The idea was not a new one, 

 for Farrer had already made the attempt. His 

 work however was pre-Mendelian and based on 

 the fact that an Fg 1 generation contained, as a 

 rule, a large number of distinct types. Amongst 

 these Farrer hoped to find some showing a greater 

 degree of rust-resistance than any of the varieties 

 he then had under cultivation. His optimism was 

 rewarded, for he found amongst them the variety 

 "Bobs" which possesses a very fair degree of resis- 

 tance to the attacks of the black rust, the common 

 species in Australia and several other important 

 wheat-growing countries, but a species of little 

 importance here at present. Farrer's experiments 

 were not planned with any object of testing the 

 possibility of definitely breeding for rust-resistance, 

 neither had he apparently satisfactory material at 

 hand for the purpose. 



The first steps in the investigation were taken 

 by comparing the rust-resistance of several hundred 

 distinct varieties of wheat grown under uniform 



1 The letter F followed by the figure i is used to denote the actual 

 hybrid plant, and successive generations raised from it are denoted 

 by F 2 , F 3 , F 4 , etc. 



