Dale— A Bacterial Disease of Potato Leaves . 141 
At 25 0 C. a fair growth developed on a streak, and a stronger develop- 
ment in a stab culture, as in the cultures at lower temperatures. 
Urea in agar . At ordinary temperatures and in the incubator good 
growths were obtained on both streak and stab. The streak culture forms 
a broad, straight, and rather wide band. The stab culture formed a film over 
the surface, and also grew down the medium in a filmy manner as in wood 
ashes in agar. 
On cane-sugar and peptone in gelatine 1 growth was very abundant. 
Large bubbles of gas were given off in such numbers as to form a frothy 
mass on the surface of the solid medium. Bubbles were also given off 
along the line of stab cultures, in spite of the solidity of the medium. As 
in other gelatine cultures, the colonies in a stab were clearly distinguishable 
with a hand lens as isolated round dots. Liquefaction here also was very 
slow and was not complete for some weeks. There is a distinct formation 
of acid, during which the neutral litmus becomes first red and then colourless. 
On sterile milk . Several tubes, prepared according to the method 
given by Percival, 1 2 were infected with the organism, and one uninfected 
tube was placed with them as a control. In the incubator, at 25 0 C., by the 
next day the infected milk was going yellow at the top. At about 13° C. 
no change was visible. On the second day the infected milk in the incubator 
was coagulated and the violet colour had disappeared. There was a yellow 
liquid at the top and an almost pure white coagulum below. The milk in 
the control tube remained unchanged. At the lower temperature of the 
room the infected milk was changing colour but was not yet coagulated. 
After some time the coagulum disappeared. 
O71 beer-wort gelatine there was very little growth, which is somewhat 
surprising as this organism grows so freely on so many media, and also 
because most organisms grow well on this particular medium. 
Aerobism. A test-tube containing a stab culture of the organism in 
cane-sugar, peptone, and gelatine was placed in a larger tube containing 
a mixture of caustic soda and pyrogallin. Growth occurred abundantly, as 
was shown by the evolution of g£s in the culture tube. 
A second experiment was made, using the method given by Pethybridge 
and Murphy. 3 A streak culture of the organism was made in agar (urea 
was used in this case) and immediately plugged with melted agar to exclude 
the air. In this tube also growth was vigorous. The organism can there- 
fore live under anaerobic conditions. 
1 This medium was made up as follows : cane-sugar 1.5% ; peptone 0-5% ; gelatine io-o% ; 
distilled water 30 c.c. ; neutral litmus. 
2 The milk was prepared as follows : Milk was passed through a separator. If not neutral 
it was rendered so, and a little neutral litmus added, which gave the milk a purple colour. The 
separated milk was sterilized in plugged tubes. Percival, Agricultural Bacteriology, 1910. 
3 Pethybridge and Murphy : A Bacterial Disease of the Potato Plant in Ireland and the 
Organism causing it. Proceedings of the Royal Irish Academy, vol. xxix, section B, no. 1, 1911. 
