52 



BACTERIA IN RELATION TO PLANT DISEASES. 



cidarum, exception being made of inoculated plant No. 4, which was allowed to stand too 

 long. Since the appearance of Greig Smith's paper I have gone over slides made from these 

 inoculated plants to see if I could have overlooked such a fungus. The red bundles contain 

 an amorphous granular substance, and sometimes bacteria, but no fungi were found. 



RELATION TO SEREH. 



Is this disease identical with Sereh, the Javanese ' ' curse ' ' of the sugar-cane ? The signs 

 are for the most part the same, i. e., red bundles, dwarfing, shortening of the internodes, 

 etiolation, sprouting of the buds, transmission through infected sets, distorted terminal 

 buds, etc. The writer has never seen the disease and so can make no personal observations. 



Janse and Kriiger consider Sereh a bac- 

 teriosis of the bundles, but speak only 

 of red gum and do not mention yellow 

 slime in the bundles, at least not in any 

 of their papers read by the writer. 

 Valeton mentions yellow gum, how- 

 ever, and states that this precedes the 

 red stain, and he appears to have given 

 more attention to histology than any 

 of his colleagues. Wakker and Went 

 are opposed to this hypothesis. Went's 

 observations in the West Indies, how- 

 ever, did not confirm him in his earlier 

 belief that a fungus, Hypocrea sacchari, 

 is the cause of Sereh, for there he ob- 

 served the same fungus on the cane 

 but Sereh was absent (verbal commu- 

 nication to the writer). Only this 

 somewhat suggestive fact seems estab- 

 ished, that Sereh is not confined to Java 

 (according to Kriiger, it occurs in Mal- 

 akka, Borneo, and Bangka),and Cobb's 

 disease is found not only in Australia but also, it is said, in Java, Mauritius, and Brazil. It 

 is very desirable that a good bacteriologist should make a careful study of Sereh. Perhaps 

 two or more different diseases are now united under this name, one of which may be Cobb's 

 disease. Query: Does Sereh occur in Australia? Went is inclined to believe that it does. 

 The subject of Sereh will be treated in the following chapter (p. 72). 



MORBID ANATOMY. 



There are no hyperplasias caused by this disease, but only occasionally roots out of place, 

 premature development of axillary buds, and certain distortions of the terminal bud which 

 might be taken for such. The disease is for the most part confined to the vascular system, 

 the bundles of which are gradually filled with the bacterial slime. Figs. 19 and 20 show this 

 very well. They were made from the Australian cane already mentioned as sent to me for 

 study. In one of these bundles all the vessels of the xylem are occupied ; in the other the 

 two larger vessels are free. The lysigenetic cavity is also filled. The phloem is not affected 

 in either, nor the tissue surrounding the bundles. Such, however, is not always the case. 

 In the upper part of the stem, just below the terminal bud, where the tissues are soft, the 

 parenchyma is also attacked and numerous bacterial cavities are formed in it. In the 



Fig. 22. 



*Fig. 22. Bacterium vascularutn occupying xylem part of bundle. Like fig. 21, but cut longitudinally. Section 

 from inoculated cane-plant No. 6 at the end of three months. Slide 310 (20, second section from left. 



