WILT-DISEASES OF TOBACCO. 



239 



The following statements are taken from the more recent paper by Uyeda (1905): 



The disease is widespread in Japan and has been known for at least 25 years, having been de- 

 scribed in 1 88 1 in Ensoroku, a book on tobacco culture. Since that time it has been written upon 

 with special reference to methods of prevention by T. Kugahara in the experiment station of Huku- 

 shiina-Ken (1891) and at about the same time by Dr. S. Hori, in the Imperial Central Agricultural 

 Experiment Station at Tokyo. 



Prof. Y. Kozai, director of the experiment station at Nishigahara, has also isolated a schizomycete, 

 which he holds to be the cause of the disease. This is the same as that described by Uyeda, who 

 did his work at that station. 



The disease is variously known to the Japanese as "stem-rot, " "black-leg, ' ' and "wilt-disease. " 

 Uyeda 's studies were begun in 1899 and continued nearly 5 years. 



The disease is widespread in the province of Hitachi, and occurs also in the province of Sagami 

 and Shinano. 



Fig. 126.* 



The signs of the disease are much like those of the Granville wilt. Compare fig. 126 with pi. 

 33, and pi. 41, figs, i, 2, 7, with pi. 42, for brown stripes on the green stems. The disease occurs 

 from June to September on plants of all ages. The first sign is the sudden wilt of the foliage, after 

 which the leaves become yellow. The stem then becomes black and the roots decay. 



When the juice from diseased plants or a pure culture of the bacillus is placed on healthy tobacco 

 leaves, they begin to blacken and to show brown spots within one or two weeks. The principal veins 

 of the leaf are then hollowed out and destroyed. The infection experiments were made on young 

 and old plants at Nishigahara. These are not described. Old leaves sometimes show wavy black 

 spots bordering the veins, where the bacteria are said to have entered by the stomata. The organism 

 often enters also by the roots or through wounds above ground. All the affected parts contain great 

 quantities of bacteria and the reaction of the fluid containing them is alkaline The bark of the stem 

 shrinks considerably as the disease progresses and black lines appear upon the surface. The tissues 



*Fic. 126. Experimental field of tobacco at Ota, Japan, destroyed by bacterial wilt. Season of 1904. (After 

 Uyeda.) 



