1921.] Barberry and the Black Rust of Wheat. 121 



cases (see below) the change took place more gradually. The 

 black resting spores remain dormant on the straw and stubble 

 through the winter, germinate in the spring and give rise to other 

 minute spores, which infect the barberry leaves, thus completing 

 the life -cycle of the fungus. 



A small point, though possibly of great practical importance, was 

 observed in connection with the summer spores. It was noted 

 that in some varieties of wheat these spores (the uredospores; 

 did not break through the epidermis of the stem. The red stage 

 was visible within the stem but it never burst through, merely 

 slowly changing to the black or teleutospore stage. Late in the 

 season, w T hen the transition from one stage to the other was 

 complete, the epidermis was ruptured and the black winter-spores 

 were exposed for dispersal. This might have been an unusual 

 occurrence due to the low temperature prevailing through the 

 summer. However, the matter calls for further investigation, 

 because, if varieties of wheat can be found in which the uredo- 

 spores are not exposed for dispersal, such varieties will not spread 

 the summer stage. Further, the rupturing of the epidermis 

 injures the wheat owing to the loss of water by evaporation, and 

 if this does not take place in some varieties until late in the season 

 these should give better yields than those in which the epidermis 

 is broken early. In short, varieties of wheat in which the uredo- 

 spore stage does not break through, the epidermis may be 

 regarded as partial "resisters." 



Spread of Disease from Barberry to Wheat. — The spread of 

 the disease from barberry to wheat was observed fairly closely 

 at two places. In one case, there were two barberry bushes in 

 ■ he middle of a hedge alongside the wheat, and in the other 

 there was a strip of barberry hedge, eight yards long, near 

 one corner of the wheat field. In both cases it was obvious 

 that the disease had commenced, and that the intensity was 

 greater, near the barberry. To one of these places tw T o farmers 

 were taken to witness this for themselves, and after going 

 carefully over the field they were fully satisfied that the bar- 

 berry was a contributing factor in disseminating the disease. 



Effect of Black Rust on Wheat Growing in South West 

 Wales. — Although this part of Wales is mountainous and not 

 considered generally suitable for wiieat mowing, there are 

 districts where wheat might be more successfully grown if it 

 were not for the presence of the barberry and the black rust 

 disease. Most of the farmers endeavour to grow enough for 

 home consumption, and many would sow more wheal if they 



