PLATE 22. 



L 



Bacterial black spot of the walnut. 



A late stage of the disease on the nuts. Photograph by Pierce. Mr. Pierce, who discovered the cause of this disease, has 

 demonstrated 50 per cent of the losses preventable by spraying, and is now endeavoring to obtain resistant varieties by 

 hybridizing and selection. The sum of $20,000 was offered by the walnut growers of California some time ago for a 

 satisfactory remedy, and recently the legislature of California has appropriated a considerable sum for its investigation. 



