. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 212 BACTERIA IN RELATION TO PLANT DISEASES. of the stem or main root; (2) A sudden wilt due to the fiUing of the vascular bundles with fungi of the form-genus Fusarinm; and (3) A wilt due to the rotting off of the main stem at the surface of the earth. This disease may be distinguished readily enough by the facts that fungi are not present and that there is no stem-injury or root-injury of the kinds just described, and also by the further fact of the invariable presence of large numbers of white, ^ sticky bacteria in the v
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 212 BACTERIA IN RELATION TO PLANT DISEASES. of the stem or main root; (2) A sudden wilt due to the fiUing of the vascular bundles with fungi of the form-genus Fusarinm; and (3) A wilt due to the rotting off of the main stem at the surface of the earth. This disease may be distinguished readily enough by the facts that fungi are not present and that there is no stem-injury or root-injury of the kinds just described, and also by the further fact of the invariable presence of large numbers of white, ^ sticky bacteria in the vascular system. These are so abundant and usually so viscid that if the tip of the finger be pressed against the cross-section of a diseased stem at once, or better,,, some minutes after cutting, and then gently removed, the bacteria will remain attached to ' the finger and string out''in numerous delicate threads (fig. 52) resembling cobwebs. For the microscopic structure of these threads consult Vol. I (fig. 14). If a little time is allowed the bacteria also ooze from the cut surface (cross-section) of such stems in milk-white drops, especially if the stems are cut a second time and the basal end put into water or moist air. The wilting and shriveling of the leaf blades always precede the destruction of the leaf- stalks and of the stem by a considerable period, so that it is common to find plants which have lost all or nearly all of their foliage while still retaining a green and normal looking stem (plate i, fig. 2), the vessels of which, however, for long distances will be found to be more or less fully occupied by the bacillus (fig. 6). In the end, petioles and stems shrivel and die, but the organism does not make its appearance on the surface of the plants and there is nothing resembling a soft wet-rot, not even in the fruits. In rather resistant plants, e. g., certain squashes, the foliage may wilt dur- ing warm, dry days and partially recover at night or during cool, mo
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