. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 2l6 BACTERIA IN RELATION TO DISEASES. to be full of bacilli. That this diluted culture was virulent is also shown by the fact that out of ID large cucumber-plants inoculated from it the same day by needle-puncture, 8 promptly contracted the disease. Up to this time therefore, the weight of the evidence favors the view that aphides do not play any part in the dissemination of this disease. Further experiments should be made. The fact that one check-plant contracted the dis- ease in some unknown way shows that at leas
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 2l6 BACTERIA IN RELATION TO DISEASES. to be full of bacilli. That this diluted culture was virulent is also shown by the fact that out of ID large cucumber-plants inoculated from it the same day by needle-puncture, 8 promptly contracted the disease. Up to this time therefore, the weight of the evidence favors the view that aphides do not play any part in the dissemination of this disease. Further experiments should be made. The fact that one check-plant contracted the dis- ease in some unknown way shows that at least occasionally the disease may be induced by simple spraying in the absence of suctorial insects, and this is what invalidates the experi- ment with the squash-bugs. Some of the sprayed plants on which they were colonized contracted the disease, but the additional inference is of the post hoc sort. The disease seems to be worse in moist, warm weather than in dry cool weather, at the same time excessively hot weather seems to be unfavorable to its spread. A soft watery condition of the tissues is believed to be favorable to the spread of this disease. In a number of instances it has been observed to do most injury in wet seasons, but it is not restricted to such seasons. Possibly, the greater injury during rainy periods is attri- butable chiefly to the greater number of infections, favored by cloud-screens and the moisture of the air. In a dry air many infected wounds probably dry out before the bacillus has secured a foothold, or are rendered sterile by sunshine. The bacillus is so well distributed that if it were not for some such re- straining circumstances it is doubtful if ordinary cucurbitaceous plants could be grown at all in the Northeastern United States. Aside from suitable weather-conditions and the propagation of extra sensitive varieties, which should of course be avoided, the conditions most favorable to the spread of this disease, so far as yet known, are the mult
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