516 DISEASES OF CULTIVATED PLANTS 



multiply, and in four days the blackness of the rootlets and 

 the stem as in the original specimens made its appearance. 

 The examination of the blackened tissues showed that the 

 injury was due to the same bacteria. A further experiment 

 was made to test whether this bacterium of the bean was the 

 same as that causing blackleg in potato. Bacteria from the 

 beans were transferred to healthy potato tubers, which were 

 planted in the soil. The shoots that were developed were 

 healthy, but after direct infection of the shoots the disease 

 appeared and they were killed. Those results may not be 

 sufficient to determine the identity of the bacterium causing 

 blackleg in potatoes and in beans ; it nevertheless establishes 

 that the potato may be infected by the bacterium from the 

 bean. It is therefore well that caution be exercised when an 

 attack of blackleg appears in a crop of either beans or 

 potatoes; neither plant should be the succeeding crop.' 



Carruthers, W., Journ. Roy. Agr. Sac. Eng., 6S, p. 226 

 (1907). 



Yellowing of beetroot leaves. Delacroix describes a 

 bacterial disease of beetroot in France, which at times causes 

 serious loss. Sugar beet and mangolds are equally attacked. 

 The disease is readily recognised by the presence of irregular 

 patches of a pale-green colour on the leaves. Numerous 

 mobile bacteria are present in the cells of such discoloured 

 patches. Similar organisms are present in the tissues of the 

 leaf-stalk, root, calyx, and fruit. The organism proved to be 

 new, and received the name of Bacillus tabificans (G. 

 Delacroix). It is shortly oval, i^xi /'. No vibratile cilia 

 or production of spores observed. 



The preventive methods suggested are: (1) A three years' 

 rotation; (2) Burn all diseased plants; (3) Only sow seed 

 that is four years old. 



Prillieux, Comp. Rend., 37, p. 871 (1903). 



Bacterial tumours of the olive. Numerous irregularly 

 globusr nodules, furnished with a central depression, and irregu- 

 larly wrinkled surface, are often present on branches of the 

 olive-tree. The branches thus attacked soon perish, and trees 

 that are badly infested are recognised at a distance by the 

 wilted, sickly-looking folinge. These nodules or tumours 

 are quite woody in consistency, and are caused by a bacterium 

 known as Bacterium savastanoi, E. F. Smith (sym. Bacillus 



