. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 3IO BACTERIA IN RELATION TO PLANT DISEASES. and thence into the stem where, in turn, the vessels of the stem are occluded and browned. Subsequently if the tissues are soft enough the organism passes up and down the stem and out into other leaves, always by way of the vascular system. The rapidity of movement in stems depends on their texture. In hard woody stems the bacteria move with extreme slowness or are entirely hemmed in; in soft juicy stems progress resembles that in the petiole. In leaves which are infected from th
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. 3IO BACTERIA IN RELATION TO PLANT DISEASES. and thence into the stem where, in turn, the vessels of the stem are occluded and browned. Subsequently if the tissues are soft enough the organism passes up and down the stem and out into other leaves, always by way of the vascular system. The rapidity of movement in stems depends on their texture. In hard woody stems the bacteria move with extreme slowness or are entirely hemmed in; in soft juicy stems progress resembles that in the petiole. In leaves which are infected from the stem (fig. 98), the entire leaf-blade may be attacked almost at once and in that case may show signs of wilting. The writer has fre- quently seen cabbage leaves become flabby, unjoint and fall off while the bacteria were still confined to the petiole, such leaves having been infected by way of the leaf-traces as the result of stem-inoculations. In these cases so many leaf-traces were involved that the leaf was unable to obtain the necessary water-supply. More often some of the leaf-traces are not involved and the leaf manages to function more or less imperfectly for a considerable time. In such a leaf a part of the veins in the leaf-blade are always blackened considerably in advance of the remainder and wilting may not occur. The writer tried passing i per cent eosine water up such petioles by transferring them to the red fluid after cutting them under water. In many cases the eosine only passed up the unob- structed vessels, but whether failure to pass up the bacterially occluded vessels was due simply to the occlusion, or must be ascribed in part to the destruction of the vessel-walls by the bacteria, was not determined. Whether the first signs on the expanded portion of such leaves are basal or terminal, or on one side or the other of the blade, depends en- tirely on which leaf-traces are entered first, dif- ferent ones ramifying to different parts of the leaf (Smith, Heck
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