THE ANGULAR LEAF-SPOT OF COTTON! CAUSE 325 



of the softened gelatin (Arizona organism) numerous spatulate 

 finger-like projections (Fig. 257). Gelatin stab cultures are 

 liquefied very slowly. In tube cultures 83 days old, one-half 

 to two-thirds only of the gelatin was liquefied. There was no 

 decided rim or pellicle, but a copious yellow precipitate, the 

 fluid gelatin remaining clear and unstained. In another year 

 (1915) tubes of + 10 peptone beef gelatin inoculated with the 

 Arizona organism by needle stabs were only one-fourth liquefied 

 after 30 days at 16 to 19C. although there was a prompt and 



FIG. 248. Flagellate rods of Bacterium malvacearum cultivated from an 

 angular leaf spot. Arizona cotton. Stained by van Ermengem's silver method. 

 X 1000. 



good growth. At the end of 60 days (same temperature) less 

 than one-half the gelatin was liquefied. 



On Loffler's solidified blood serum, there is a copious growth 

 (paler yellow than that of Bacterium phaseoli) with slow lique- 

 faction. At end of 15 days in tubes containing Bacterium 

 phaseoli all the substratum had changed color (darkened) and 

 most of it had liquefied; whereas in tubes containing Bacterium 

 malvacearum there was very little change in color (the bulk 

 white) and not one-twentieth part had liquefied. At the end of 

 30 days the difference in color and amount of liquefaction was 



