Pethybeidge anij Murphy — Bacterial Disease of the Potato. 25 



considerable time very little sediment is found in the bottom of the tube. At 

 25'^ C. the growth is but little, if any, more pronounced. No characteristic 

 odour is produced ; but broth, which is neutral to litmus at the start, remains 

 neutral. No traces whatever of the formation of a pellicle were ever observed. 



(13) Ghicose Broth, 2 |jer cent. — At 25° C. growth is considerably more 

 profuse than in ordinary broth at the same temperatiu'e. The turbidity is 

 well marked ; and a fair- amount of deposit settles down in the tube. In a 

 fermentation-tube with one arm closed, gas is produced in small amount, but 

 quite constantly. The reaction of the broth is changed from that of slight 

 alkalinity to that of distinct acidity. 



(14) Cane-Sugar Broth, 2 2Jer cent. — The growth here is very similar to that 

 in glucose broth. Both gas and acid are produced. 



(15) Lactose Broth, 2 per cent. — Growth here is also similar to that produced 

 in the presence of the other two sugars. A rough quantitative analysis of the 



CO 1 



gas produced was made here, and the proportions found to be -~ = t • 



(16) Potassium Nitrate Broth, 2 per cent. — Growth is slightly better than 

 in ordinary broth at 25° C. After forty-eight hours nitrites were present 

 (KI and starch test, with control) ; and they were still present after a period 

 of thirty-three days. Wlien a plug of vaseline was left on the surface of the 

 inoculated broth, gas was always produced (controls treated similarly gave no 

 trace of gas) ; but the amount of it was always small and the pressure developed 

 never sirfficient to push the vaseline up the tube. The broth, which was 

 neutral at the start, became alkaline. 



[11) Glycerine Broth, 2 per cent. — Growth at 25° C. is but poor, only a slight 

 sediment being produced. No gas is formed in a fermentation-tube, and no 

 acidity develops. 



(18) Sterilized Potato-juice {Appel's). — Active growth occm's within twenty- 

 four hours at 25° C. ; the liquid becomes turbid, and a brownish fiocculent deposit 

 settles down in the tube. The neutralised juice becomes distinctly acid. There 

 is no trace of pellicle-formation. 



(19) Sterilized Potato-juice + 2 per cent. Glucose. — Growth very similar to 

 that in the juice without glucose. Acid is produced, but no gas. Pellicles 

 absent. 



(20) Sterilized Potato-juice + 2 per cent. Cane Sugar. — Similar to (19). 



(21) Glucose-agar and Gane-Sugar-agar Shake-Cultures. — Gas-bubbles are 

 produced in both cases. 



(22) Agar superimpiosed over Agar Stab. — Growth along the stab and 

 between the two masses of agar; hence the organism is not particularly strongly 

 aerobic. 



K.I.A. PEOC, VOL. XXIX., SECT. B. [-D] 



