378 Annual Report for 191 \ of the Botanist. 



the almost complete lack of potato disease {Phytophthora 

 infestans), of which not a single specimen was sent in to the 

 Department. Wheat rust {Puccinia gluniaruni) was also far 

 less common than normally. On the other hand the mildews 

 appear to have been especially abundant throughout the 

 summer and autumn, for nearly half of the diseases sent in for 

 determination were caused by these parasites. They included 

 six cases on swedes, three on wheat, three on apple foliage, two 

 on barley, two on peaches, one on hawthorn, and one on oak. 

 Apple scab {Fusicladiuni dendriticum) also api)ears to have 

 been very prevalent. 



A Member in Norfolk who sent specimens of mangolds in 

 the previous year bearing tumour-like outgrowths again for- 

 warded specimens, and it was possible to make a more detailed 

 examination of the disease. There is now no doubt that it is 

 the crown gall, caused, as Erwin Smith has proved lately, by 

 Bacterium tumefaciens (Bull. 213, Bureau of Plant Industry, 

 Washington). A partial description of the disease has also 

 lieen given in the Journal of the Board of Agriculture (Vol. 17, 

 page 830). 



The disease may possibly prove serious, as it is capable of 

 attacking an unusually wide range of plants, such as sugar-beet, 

 hops, chrysanthemums, vines, roses, and apples. It appears 

 to be fairly common on the Continent on sugar-beets. At 

 present it is not generally distributed in this country, and 

 the only outbreaks I have been able to trace with cer- 

 tainty have occurred in Norfolk and Shropshire. In each 

 case there is some evidence to show that the introduction 

 of Continental sugar-beet seed has been responsible for its 

 presence. 



If infected plants are destroyed, preferably by burning, as 

 soon as the symptoms of disease are noticed, it should be 

 possible to prevent it from obtaining a hold in the country. 

 The illustration will show these characteristic symptoms with 

 sufficient clearness. The outgrowths are at first firm and have 

 much the same texture and markings as the mangold itself. 

 As the roots mature, and particularly when stored, the mass 

 becomes darker and not unlike water-sodden peat. Apart 

 from this, however, such roots keep fairly well. 



A somewhat similar disease was received from a correspon- 

 dent in Cambridgeshire. In this case the roots of raspberries 

 were attacked, and striking bead-like tumours produced. 

 Microscopic examination showed no signs of fungus hypha3 in 

 the tumours, but ultimately bacteria were found in their 

 woody-diseased tissue. Whether these are identical with Bad. 

 timiefacietis can only be decided by infection experiments next 

 season. 



