32 A SOFT EOT OF THE CALLA LILY. 



extended a little farther from the edge. At the end of eight days 

 from tlu> l)oginning of the experiment the color had entirely' disap- 

 peared from the inoculated tubes, while it remained unchanged in the 

 controls. The lead-acetate papers Avere blackened about three-fourths 

 of an inch from the lower end upward, the color fading out and leav- 

 ing no sharp line of demarcation. The liquid that settled in the angb 

 of the inoculated tubes at the end of eight da)^s had become nearly 

 cream color, corresponding closely to Ridgwa3^'s No. 20, Plate VI, or 

 Saccardo's Cremeus, No. 27, Table II, while in the control tubes the 

 liquid was still litmus color. At the expiration of twenty-seven days 

 from the beginning of the experiment the color began to return in the 

 agar, and seven days later the original color had returned throughout 

 the agar and also in the liquid that had previoush^ been cream color. 

 As soon as the color began to return to the agar the discoloration of 

 the lead-acetate slips ceased to develop. The black color in the lead- 

 acetate papers was undoubtedly due to the formation of hydrogen sul- 

 phid, which develops on certain media during the activity of the calla- 

 rot organism. As soon as the organism became inactive the hydrogen 

 sulphid ceased to form, and what had formed passed off from the agar, 

 allowing the litmus color to return. Beef broth inoculated Avith the 

 calla-rot organism discolored the margins of lead-acetate paper in 

 twentj'-four hours, the discoloration extending about one-fourth of an 

 inch from the margin. This gas forms much more rapidly in beef 

 broth than in litmus-lactose agar, while the organism growing on 

 potato cylinders produced no blackening of lead-acetate strips, even at 

 the end of three weeks after inoculation. 



INDOL. 



Several tubes of peptonized Uschinsky's solution Avere inoculated 

 Avith fresh cultures of the calla-rot organism. The inoculated tubes 

 clouded Avithin tAventy-four hours, and tests Avere made from day to 

 day for indol, using concentrated sulphuric acid and sodium nitrite, 

 but even at the end of twentA^-four days no trace of indol could be 

 detected, although the tubes Averc heated to 80° C. after the application 

 of the acid and the nitrite. 



XITRATKS RKDUCKl) TO MTRITES. 



Four tul)es of nitrate bouillon were inoculated Avith the calla germ. 

 These became distinctly clouded in the usual time, and at the end of 

 tAvo days were tested for nitrites as follows: To 10 c. c. of the clouded 

 bouillion 1 c. c. of starch solution and 1 c. c. of potassium iodid solu- 

 tion were added. One drop of sulphuric acid was then sufficient to 

 giA'e an intensely ))lue color, indicating that the nitrates had been 

 chanp-ed to nitrites. The control tubes treated in the same manner 

 gaA'e no reaction. 



