Jan. is, 1917 
Blackleg Disease of Potato 
113 
To save unnecessary repetition it may be stated in the beginning that 
the two organisms received and carried under the name of B . phytoph - 
thorns produced no gas or acid in the presence of any of these substances 
and imparted a slight alkalinity to the culture medium. The one 
received from Dr. Appel in no case produced any visible clouding of the 
closed arm of the fermentation tube. The one received from Dr. Schuster 
produced a delayed clouding of the closed arm in all cases except with 
glycerin, but even with this the clouding was later nearly as complete 
as in the bulb. 
The results obtained with the remaining organisms—namely, B. atro- 
septicus, B . solanisaprus , B. melanogenes, IIIA, SE, IIP—were alike and 
constant with regard to gas formation, growth in the closed arm, and 
production of acid. On repeated trials they all invariably produced gas 
in the presence of dextrose, saccharose, lactose, maltose, and mannit. 
They produced no gas from glycerin and dextrin. With dextrose this 
amount of gas was small, ranging from 3 to 5 per cent. With saccharose 
the percentage of gas was higher, usually being from 7 to 9 per cent. 
Except with glycerin, there was always a prompt clouding of the closed 
arm, though this was usually less than in the bulb. This clouding in 
the closed arm was persistent, although a slight clearing at the top of the 
tube was observed in old cultures containing maltose. Add was pro¬ 
duced in the presence of all the carbohydrates used. 
Very little of the gas which was formed was absorbed by a 2 per cent 
solution of sodium hydrate. The remainder of the gas was explosive. 
When expressed in the terms of H:C 0 2 , as accurately as could be deter¬ 
mined, this varied from 1: o to 5 or 6:1. No attempt was made to deter¬ 
mine further the nature of this gas. Gas in all cases usually appeared 
on the second or third day and reached its maximum before the tenth, 
usually on the sixth or seventh. 
It will be noted that this constant appearance of gas in dextrose, 
saccharose, and maltose with B . solanisaprus was contrary to Harrison's 
original description (17). Likewise the production of gas with B. atro- 
septicus from lactose and dextrose differs from the results recorded by 
Van Hall. In gas production B . melanogenes agreed in every respect to 
Pethybridge and Murphy's description (26). 
In neutral-red lactose fermentation broth the amount of gas obtained 
in each case with the 6 different organisms was the same as with the 
ordinary lactose broth. In 48 hours the entire contents of the tube 
appeared distinctly more red than the check. On the third day the 
closed arm took on a yellowish olive tinge, which later changed to a 
canary-yellow, stronger even than that produced by B. coli f run at the 
same time for comparison. This color persisted for one month, or as 
long as the cultures were under observation. During the same time the 
bulb showed a more pronounced red than the check tube. 
