STUDIES UPON THE BLACKLEG DISEASE OF THE 
POTATO, WITH SPECIAL REFERENCE TO THE RELA¬ 
TIONSHIP OF THE CAUSAL ORGANISMS 
By W. J. Morse, 
Plant Pathologist, Maine Agricultural Experiment Station 
HISTORICAL REVIEW 
The fact that the potato ( Solarium, tuberosum) is subject to maladies 
like that under consideration in this paper was noted at a comparatively 
early date in the literature of bacterial diseases of plants. De Jubain- 
ville and Vesque (8) 1 mentioned in 1878 a “cellular-rot” of potatoes, 
radishes, carrots, and beets as occurring in the soil and in cellars; but 
bacteria are not mentioned as the cause. Their paper and the one 
following are reviewed by Smith (32). 
In 1879 Reinke and Berthold (30) pointed out quite clearly that a 
wetrot of potatoes could occur without the presence of any fungi. 
According to Smith, they apparently did not have any active parasite 
and did not work with pure cultures. However, they were able to 
inoculate and cause a decay of healthy tubers by means of the watery 
fluid taken from diseased potatoes, provided especially favorable condi¬ 
tions were supplied in the line of moisture. They were also able to 
demonstrate the constant association of bacteria with the wetrotting 
of the tubers. 
Prillieux and Delacroix (28) described a disease of the potato stem 
from France in 1890 and gave the name “ Bacillus caulivorus” to the 
organism which they considered to be the cause. Nothing is said in 
this paper as to the isolation of the organism and the growth of it in 
pure cultures, although later Prillieux (27, v. 1, p. 16) credits it with 
producing a green coloration of certain culture media. Prunet (29), who 
reviewed the literature on this subject in 1902, called attention to the 
fact that Laurent (21) had stated in 1899 that B. caulivorus was prob¬ 
ably nothing other than B . fluorescens liquefaciens Fliigge, a common 
soil saprophyte. Pethybridge and Murphy (26), who have more recently 
written on the subject, state that— 
Later on Delacroix, in dealing with B. caulivorus, speaks of it as most probably 
identical with Bacillus fluorescens liquefaciens Fliigge, a common saprophytic form, 
which, he suggests, may perhaps under certain special conditions become parasitic. 
It is evident that Prillieux and Delacroix (28) did not secure the 
organism responsible for the disease. However, there is every reason 
to believe that they were concerned with a malady similar to that under 
1 Reference is made by number to " Literature cited,” pp. 124-126. 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. VIII, No. 3 
Jan. is, 1917 
