New York Agricultural Experiment Station. 405 



species is constantly associated with the disease and fungous 

 hjphse are to be found on the interior of the stem only in decayed 

 specimens. A pink Fusarium grows in great profusion on the 

 sheathing bases of the leaves and Epicoccum neglectuin Desm. is 

 common on the dead leaves, but both of these fungi are sapro- 

 phytes and do not appear until the leaves are dead. 



The yellow mass of baeteria in the vascular system becomes 

 an object of suspicion as soon as it is observed. These bacteria 

 make their appearance before the plant commences to wilt and 

 by the time the plant is wholly dead the vessels are gorged with 

 them. If the bacteria have nothing to do with the disease how 

 can their presence be explained? Russell* has shown that " nor- 

 mally, the healthy plant, with intact outer membranes, is free 

 from bacteria within its tissues." Concerniug the possibility of 

 saprophytic bacteria gaining access to healthy plant tissue 

 through the medium of wounds, the same author reports experi- 

 mentsf in which it was shown that, although certain saprohytio 

 species are capable of spreading through healthy tissue^, they do 

 not penetrate to any great distance nor multiply rapidly. There- 

 fore, on account of the immense numbers of the corn bacterium 

 which may be found throughout the vascular system of every 

 affected plant, even in tlie early stages of the disease, and its 

 scarcity in the tissues of vigorous, healthy plants, coupled with 

 the fact of the absence of any other sufficient cause, it is safe 

 to assume that the yellow bacterium is the cause of the trouble. 

 Conclusive proof of this, however, is to be obtained only from 

 inoculation experiments. 



ISOLATION OF THE GERM. 



Pure cultures of the germ are easily obtained. It grows read- 

 ily, at a temperature of from 21° to 28°C., on neutral beef agar, 

 neutral potato agar or neutral gelatin. By carefully splitting 

 open the stem of a freshly wilted plant and touching a sterilized 

 platinum needle to one of the bacteria-laden vessels it is quite 



♦RusseH, H. L. Bacteria in Their Relation to Vegetable Tissue. A dissertation pre- 

 sented to the Board of University Studies of the Johns Hopkins University for the 

 degree of Doctor of Philosophy. Friedenwald Company, Baltimore, 1892, pp. 3-6. 



t Non-Parasitic Bacteria in Vegetable Tissue. Bot. Gazette, Vol. XVIII, pp. 93-96. 



