120 
Journal of Agricultural Research 
Vol. VIII, No. 3 
tance of 3 to 4 inches and finally fully decayed and cut off, resulting in 
the death of that part of the plants above the points of inoculation. 1 
As has been clearly indicated in the previous pages, inoculations of 
potato stems and tubers with the cultures received and carried under 
the name of B . phytophthorus produced no disease whatever. The punc¬ 
tures into which the cultures were inserted dried out rapidly and were in 
every way similar to those into which sterile broth or distilled water had 
been inserted as checks. 
Some work was done to test the pathogenicity of the strains used, upon 
plants closely related to and unrelated to the potato. It will be unnec¬ 
essary to go into the details of this since the present studies are pri¬ 
marily concerned with a comparison of the various morphological, cul¬ 
tural, physical, and biochemical features of the different organisms. 
group numbers 
The numerical system employed in the descriptive chart or card 
adopted by the Society of American Bacteriologists furnishes a means 
whereby a considerable number of contrasted, salient characters may be 
brought together in a small space to facilitate comparisons. This 
decimal system of group numbers is useful as a quick method of showing 
close relationships and important differences within the genus, but is not 
a sufficient characterization for any organism. However, it does record 
in a very compact manner many of the important differential characters. 
GROUP NUMBERS BASED ON THE PRESENT STUDIES 
B. atrosepticus Van Hall... 221. 1113522 
B. solanisaprus Harrison..... 221. 1113522 
B. melanogenss Pethybridge and Murphy.. 221. 1113522 
IIIA. 221.1113522 
SE. 221.1113522 
IIP.. 221.1113522 
B. phytophthorus ( as received from Appel).. 222. 3333033 
B. phytophthorus (as received from Schuster).221. 3333533 
Some question might be raised with regard to whether the figure in 
the fifth place to the right of the decimal point in the first six group num¬ 
bers should be a 5 or a o. Here the only yellow color that developed was 
on potato, and this was by no means strong. It is possible also that the 
next figure to the right in the same group numbers should be 3, for the 
diastatic action on potato starch is doubtful. 
1 The writer has no explanation to offer for this unexpected manifestation of pathogenicity on the part 
of this'culture of B. atrosepticus. The system used in keeping and transferring the stock cultures is such 
that any possibility of getting the different strains mixed is practically eliminated. The fact that the stock 
cultures have always been carried in beef broth with occasional transfers to potato broth may have some¬ 
thing to do with it. Others who have kept their stock cultures of these and the closely related softrot 
bacteria of the B. carotovorus type on agar have reported loss in pathogenicity. Including those mentioned 
in this paper the writer has carried over 20 different strains of blackleg organisms for from 5 to 9 years, but 
with no permanent evidence of loss of pathogenicity with any. 
