Fungous diseases of plants . nd the pathological effect is there-fore due, in large part, doubtless, to cutting off the transpirationstream. If there are secondary effects felt in the protoplasm ofrather distant living cells, and brought about by diffusion of inju-rious excreted substances, it has not been demonstrated, so far asI am aware, in the case of any bacterial disease of plants. Fieldcorn and pop-corn are resistant, but inoculation experiments with Sweet Corn, showing Bundles occu PIED BY Bacterial Colonies. (Photo graph by F. C. Stewart) SCHIZOMYCETES. BACTERIA 113 sweet corn have be
Fungous diseases of plants . nd the pathological effect is there-fore due, in large part, doubtless, to cutting off the transpirationstream. If there are secondary effects felt in the protoplasm ofrather distant living cells, and brought about by diffusion of inju-rious excreted substances, it has not been demonstrated, so far asI am aware, in the case of any bacterial disease of plants. Fieldcorn and pop-corn are resistant, but inoculation experiments with Sweet Corn, showing Bundles occu PIED BY Bacterial Colonies. (Photo graph by F. C. Stewart) SCHIZOMYCETES. BACTERIA 113 sweet corn have been successful. The organism is probably spreadby many mechanical agencies, and also distributed clinging to theseed. The organism, morphology and reactions. The rods arc short,almost ovoidal in form, ordinarily x . On agarthe colonies are more or less circular, becoming lobulated at themargins. With age the surface is granular. The color changesfrom yellowish white to bright yellow. Gelatin is not liquefied. A. Fig. 27. LuNGiTuuiNAL Section of Stalk of Sweet Corn,SHOWING A Diseased Bundle. (Photograph by F. C. Stewart) vigorous growth is produced on steamed potato, which in a weekis iridescent. The potato turns brown in time. In bouillon a turbidity is produced, and gradually a yellowish-white precipitate is formed. Yellow, surface-colony globules Uschinskys solution there is a vigorous growth, litmus milk isslowly decolorized, and there is no coagulation. Gas is not pro-duced, and the organism is aerobic and facultative anaerobic. Control measures. There is great difference in the susceptibilityof varieties of sweet corn, and this may be made use of wherenecessary. Only sound seed from uninfested regions should beemployed. A rotation of crops is also an important precautionarymeasure. 114 FUNGOUS DISEASES OF PLANTS IV. CROWN GALL OF APPLE, PEACH, AND OTHER PLANTSPseudomoiias tumefaciens Erw. Smith and Townsend ^ Hedgcock, Geo. G. Crown Gall, Hairy Root
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