S. p. Armstrono 65 



The followiiifi records illustrate the progress of tlie rust attack during 

 1918: 



The autumn sown poi'tion of the F., crop contained 829 plants, of 

 which 627 were finally I'usted. Of these "finally rusted" individuals, 

 54 per cent, were attacked by June 10th to 13th; 90 pei' cent, by June 

 29th; and 100 per cent, by July 30th. 



The progress of the rust attack in 1918 is further illustrated by the 

 notes on the two varieties given below. 



Willtelmiiin. (01 plants). 



iVIay 18th, a little rust seen. 



June 1st, 23 per cent, of the plants slightly rusted. 

 June 8th, 81 per cent, of the plants rusted. 

 June 21st, 100 per cent, of the plants rusted. 



Extra Squarehead II (29 plants). 



April 8th. one pustule on the culture. 



May 18th, a few jjlants shghtly rusted. 



June 1st, 34 per cent, of the plants slightly rusted. 



June 8th, 65 per cent, rusted. 



June 21st, 100 ^Jer cent, rusted. 



These observations show that Yellow Rust spread most rapidly in 

 1918 during the last week in May and the first three weeks in June. 



(C) Results obtained in the F^ f/eneralio)) (1918). 



From the middle of March onwards all the F^ plants and the parent 

 cultures were kept under observation. By June 8th over 80 per cent, of 

 the plants in an adjacent plot of Wilhelmina wheat were rusted, and it 

 was therefore decided to start at once a .systematic examination of the 

 ^2 plants. 



The method of recording results was as follows: 



Each plant received a number to indicate the number of the i-ow and 

 also its position in the row: e.g. 40/10 referred to the tenth plant in 

 the fortieth row, and so on. This made all subsequent references easy. 

 Each plant was then carefully examined leaf by leaf, and the presence 

 or absence of rust attack entered in a note-book according to the 

 previously mentioned scale. 



The autumn sown plants were examined in this way at three different 

 periods, viz. First, from June 10th to 13th; agaiti from June 29th to 

 July 3rd; and lastly, from Jidy 30th to August 3rd. 



Journ. of Agric. Soi. xii 5 



