. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. REACTION OF THE PLANT. 91 shallow, no gall results. In the crown-galls, growth may begin, it would seem, in the inner wood, in the cambium ring, in the outer bark, or in the mesophyll of a leaf, i. e., wherever cells are naturally dividing. The division of cells may take place so rapidly that all or a large part remain small. The earliest stages of the tumor formation have not been traced in serial sections. vSoon more definite information will be available. In sections of young crown galls mounted unstained in sterile wat
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. REACTION OF THE PLANT. 91 shallow, no gall results. In the crown-galls, growth may begin, it would seem, in the inner wood, in the cambium ring, in the outer bark, or in the mesophyll of a leaf, i. e., wherever cells are naturally dividing. The division of cells may take place so rapidly that all or a large part remain small. The earliest stages of the tumor formation have not been traced in serial sections. vSoon more definite information will be available. In sections of young crown galls mounted unstained in sterile water small clumps of bac- teria may sometimes be seen inside of unbroken ceHs and moving granules and rod-shaped bodies in small numbers some of which have appeared to be self- motile, the longer ones flexuous and occasionally one constricted in the middle, but stained slides have thus far given no clear-cut pictures. HYPERTROPHIES. In hypertrophied tissues the in- dividual cells are larger than normal. Usually both hyperplasia and hyper- trophy occur in the same growth, e. g., in olive-tubercle. Good ex- amples of hypertrophied cells occur also in root-nodules of IvCguminosae. Here their volume may become many times that of the normal cell. Hunger pointed out that tyloses are very common in the vessels of plants attacked by Bad. solana- ccarum, and ascribed their forma- tion to the presence of the bacteria. Of the correctness of this view I have since satisfied myself. The writer has seen the same thing in the wood of young shoots of the mul- berry attacked by Bad. mori (fig. 30). Here the stimulus to growth appears to be due to poisonous products absorbed by the vessels of the plant in advance of the move- ment of the bacteria. This is quite in accord with what we know of the action of many poisons, minute doses stimulating and larger doses destroying. The formation of tyloses in the manner described raises the question whether they may not be formed often under the stimulus of
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