Jan, is, 1917 
Blackleg Disease of Potato 
95 
Maine, in order to show that these were probably identical with each 
other and very closely related to B. solanisaprus three of these represent¬ 
ing isolations made from diseased plants from widely different parts of 
the State were selected for detailed study and an attempt was made to 
obtain all of the available named species for comparison. The names 
of the organisms thus secured and the sources from which they came 
are given in a later section. 
While the work was in progress, Smith (33) published his report on his 
studies of B . phytophthorus , mentioned below. It should be noted here 
that while he did not at this time publish in detail on his findings with 
regard to B . solanisaprus he states that: “ Bacillus solanisaprus Harrison 
is a very closely related, but not identical organism, causing a similar 
disease in potatoes.” In a letter to the writer, about two weeks before 
this paper was read, dated December 18, 1909, he stated that he had for 
three years been making a comparative study of B. phytophthorus , B. 
solanisaprus , and B. solanacearum . It is evident then that the sentence 
quoted above was based upon a series of long and careful comparative 
studies. Therefore the writer is warranted in the beginning in assuming 
that, while very closely related, there are in the opinion of Smith at 
least two separate types or species to be considered. 
For the purpose of comparison it seems necessary to state as briefly 
as possible, without sacrificing accuracy of statement, the descriptions of 
the four previously named species which have been included in the 
present comparative study with the organisms isolated in Maine by the 
writer. For convenience, since Smith's description of B. phytophthorus 
(33) is more recent than Appel's, and since Harrison's (17) is the first 
extended and most complete description of the type of the organism 
that the writer has found in Maine, these will first be given in detail, 
followed by a brief statement of the characters by which the descriptions 
of B . atrosepticus and B . melanogenes would appear to differentiate the 
last two named from each of the first and from each other. 
description op organisms previously described 
smith’s description op bacillus PHYTOPHTHORUS APPEL 1 
The organism is a non-sporiferous rod, variable in length, usually occurring singly or 
in pairs, but also forming chains of several individuals; taken from young agar cultures 
the diameter is about 0.6 to o.8,u, the length 1.5 to 2.5^ ; actively motile by means of 
peritrichiate flagella; stains readily with ordinary stains, but not by Gram’s method; 
rots potatoes (stems and tubers), cucumbers, tomatoes, etc.; aerobe and facultative 
anaerobe; organism grayish white on agar and slightly bluish opalescent by trans¬ 
mitted light; surface colonies, on thinly sown +15 agar, 1 mm. or less in diameter in 48 
hours at 20° to 23 0 C., 2 to 3 mm. broad in 4 days; round, smooth, wet-shining, inter¬ 
nally reticulated at first, amorphous under 16 mm. and 12 ocular, or with small flocks 
in the older portion; the buried colonies appear brownish under the microscope, also 
1 Quotation 748 from a paper read at the meeting of the American Phytopathological Society, Boston, 
Dec. 30 and 31, 1909. (33-) 
