. Agricultural bacteriology; a study of the relation of germ life to the farm, with laboratory experiments for students, microorganisms of soil, fertilizers, sewage, water, dairy products, miscellaneous farm products and of diseases of animals and plants. Bacteriology, Agricultural. 322 THE PARASITIC DISEASES OF PLANTS at the same time indicate how conclusive is the proof of the agency of bacteria. For this purpose will be chosen the black rot of the cabbage, cauliflower, turnip, and several other members of the family Cruciferce, The disease appears first, as a rule, upon the edges of the lea
. Agricultural bacteriology; a study of the relation of germ life to the farm, with laboratory experiments for students, microorganisms of soil, fertilizers, sewage, water, dairy products, miscellaneous farm products and of diseases of animals and plants. Bacteriology, Agricultural. 322 THE PARASITIC DISEASES OF PLANTS at the same time indicate how conclusive is the proof of the agency of bacteria. For this purpose will be chosen the black rot of the cabbage, cauliflower, turnip, and several other members of the family Cruciferce, The disease appears first, as a rule, upon the edges of the leaves, as brown spots, that spread down the leaves following the veins to the midrib and petiole and finally into the main stem of the plant. It then travels rapidly through the whole plant causing the leaves to wilt, turn yellow, dry up and become thin and parchment like. The veins in the leaves and stem are particularly affected and turn black, this being the characteristic feature of the disease and the source of the name black rot (Fig. 52). Sometimes the veins alone are affected. Sometimes the trouble does not appear in the growing plant, but only in the cabbage after storing, extend- ing through them rapidly and ruining them. When these black veins are studied with the microscope they are found to be filled with bacteria and it is easy by proper methods to remove them and cultivate them in the laboratory. Pure cultures of an organism are thus obtained, Pseud, campestris (Fig* 52). It is easy to keep this growing in the laboratory for months under strict observation. Having thus obtained a pure culture it can be demonstrated at any time that it will produce the disease. It is only necessary to dip the tip of a needle into the pure culture and then prick the leaf of a healthy plant with it. This inoculation is followed in a few days by the appearance of the characteristic symptoms of the disease, starting at the point. Fig. 52.—The black rot of cabbage. a, a bit of the stem
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbacteriologyagricult
