550 RESEARCHES ON FUNGI 



At Assiniboine Park, Winnipeg, in the middle of June, 1918, 

 some three thousand Barberry shrubs {Berberis vulgaris) became 

 very badly infected with Puccinia graminis, so that the leaves 

 (Fig. 225) were discoloured with orange aecidiospore-pustules. In 

 a letter to the Manitoba Free Press, I called attention to the danger 

 to which the wheat-fields were exposed in consequence of the 

 existence of these diseased shrubs. The result was that the Parks 

 Board of the City of Winnipeg, acting with great promptitude, dug 

 up all the shrubs within one week and burnt them. Before this 

 destruction took place, however, I used the opportunity presented 

 by the abundant fungus material to calculate the number of aecidio- 

 spores which the infected bushes were producing. 



A single aecidium produced about 11,000 spores. This I found 

 by counting the number of aecidiospore rows and the number of 

 aecidiospores in each row in individual aecidia, and by then making 

 a simple mathematical calculation. Now a single large pustule 

 upon one of the Barberry leaves often contained 150 aecidia and a 

 medium-sized pustule 50 aecidia (Figs. 225, 226). A large pustule 

 therefore produced about 1,650,000 spores and a medium-sized 

 pustule 550,000 spores. However, on each leaf, there were often 

 several pustules. The number of aecidiospores produced on each 

 leaf was therefore often several millions. 



The number of spores produced on three well-infected living 

 leaves was specially investigated. 



The first leaf bore 17 small pustules. These, collectively, con- 

 tained 336 aecidia, the number of aecidia in the 17 individual 

 pustules being as follows : 35, 33, 32, 31, 31, 30, 28, 21, 16, 14, 

 13, 12, 11, 10, 8, 7, and 4. Reckoning 11,000 aecidiospores to each 

 aecidium, the total number of aecidiospores produced by the leaf was 

 3,700,000. 



The second leaf bore 7 large pustules and 3 smaller ones. These, 

 collectively, contained 493 aecidia, the number of aecidia in the 10 

 individual pustules being as follows : 97, 74, 70, 63, 62, 47, 44, 29, 4, 

 and 3. Reckoning 11,000 aecidiospores to each aecidium, the total 

 number of aecidiospores produced by the leaf was 5,400,000. 



The third leaf bore 3 very large pustules and 9 smaller ones. 

 These, collectively, contained 732 aecidia, the number of aecidia 



