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CROWN-GALL OF PLANTS. 



EXPERIMENTS WITH LITMUS-MILK CULTURES. 



August 2-3, 1910. 



Experiments to ascertain the behavior of the various strains of 

 crown-gall organisms in milk gave the results shown in Table XII: 



Table XII. — Shotving reactions of crown-gall organisms in sterile lavender-blue litmus 



milk at 30° ('. 



August 13, 1910. 



The litmus-milk cultures now fall into three distinct groups, as 

 follows (temperature 28° to 30° C.) : 



(a) Litmus a uniform gray; milk fluid, no separation of whey, 

 moderate rim, heavy white ])ellicle, moderate white precipitate: 

 Flats poplar, peach, old rose, cotton, hop, old daisy, turnip No. 1. 



{h) Litmus distinctly reddened, most at top: Old apple, quince, 

 arbutus, Newport poplar No. 2. 



In the first two the casein has been thrown down, the bulk of the 

 fluid being whey which, together with the clot, is now nearly color- 

 less, i. e., only pinkish, with more evidence of solution of the curd in 

 quince than in old apple. In the other two the milk is still fluid, i. e., 

 no separation into curd and whey, and not yet much reduction. 



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