9 8 
Journal of Agricultural Research 
Vol. VIII, No. 3 
phate (K 2 HP 0 4 ), i per cent peptone, and 3 per cent, respectively, of different carbo¬ 
hydrates gave the following results in three successive trials: Saccharose, 0.1,0, 0.2; 
glucose, o, o, 0.1; lactose, o, o, o; mannit, 0.4, 0.6, 0.3; glycerin, o, o, o; galactose not 
changed; nitrates reduced to nitrites; reduction of methylene blue weak; sodium 
selenite reduced very rapidly; indol production not observed. Growth in bouillon 
acidulated till the reaction is 0.5 per cent normal with citric and malic acids does not 
stop growth, but 1 per cent entirely prevents it. Thermal death point for a 24-hour- 
old culture between 51 0 and 52 0 C. Optimum temperature not accurately determined, 
but strong growth takes place at 27 0 C. Readily killed by drying. 1 Pathogenicity 
to potato stems and tubers somewhat variable, but apparently imperfectly tested. 
BACILLUS MELANOGENES PETHYBRIDGE AND MURPHY 
Pethybridge and Murphy described their organism in considerable 
detail (26), but it is sufficient for our present purpose to simply state 
wherein they found it to disagree with published descriptions of pre¬ 
viously described organisms. They stated that it was larger in size than 
B. atrosepticus (0.7 to 0.9 by 1.3 to i. 8 p) and instead of occurring chiefly 
singly was found more frequently in pairs, also that its action upon milk 
appeared to be different. As contrasted with Harrison's description of 
B. solanisaprus , it possessed less flagella, formed gas in glucose and cane 
sugar, did not form a distinct ring on the surface of potato juice, and did 
not produce a raised, creamy white growth on cooked potato. They stated 
that their organism showed marked resemblance to B . phytophthorus and 
that they were strongly tempted to regard it as only a variety of the latter. 
However, it did not produce a pellicle on Appel’s sterile potato juice, and in 
nitrate broth it produced a small quantity of gas. In milk it caused the 
separation of the curd as a not very compact mass and produced a dis¬ 
tinct acidity in a comparatively short time. According to Appel’s 
description, B. phytophthorus produces a strong pellicle on sterile potato 
juice, apparently produces no gas in nitrate broth, and causes milk to 
change only on long standing, forming then a compact cylinder of pre¬ 
cipitated curd, and giving a reaction which is amphoteric to litmus. 
SOURCES OR THE CULTURES USED 
Blackleg was first observed by the writer in Maine at Sherman, on 
July 30, 1907. It was seen later at Orono and Dover; but in all cases the 
disease was in its last stages, and attempts to isolate the causal organ¬ 
ism that season resulted in failure. 
In 1908 diseased plants were obtained from Dover, Piscataquis County, 
on July 24, which showed the affected tissues filled with actively motile 
bacteria. Several subcultures were made from plates poured from these 
stems and all proved to be nonpathogenic. 
At the same time the diseased portions of the stalks were mashed up 
with distilled water in a mortar. Healthy potato tubers, bearing shoots 
1 The author also presents considerable data relative to experiments conducted to determine the avail¬ 
able sources of nitrogen and carbon, using a considerable number of different substances, apparently added 
to the culture medium singly or in combination. 
