Jan, 15,1917 
Blackleg Disease of Potato 
105 
Table II .—Measurements {in microns) of each organism arranged according to method 
of staining —Continued 
CARBOL FUCHSIN 
Organism. 
Width. 
Length. 
Average size. 
B. atrosepticus . 
0. 4 to 0. 7 
. 4 to .6 
.4 to .7 
.5 to .8 
.4 to .7 
.4 to .7 
. 4 to .6 
I. 4 to 2. I 
x. 0 to I. 9 
I. 2 tO 2 
1. 3 to 2. 5 
1. 3 to 2. I 
1. 3 to 2. I 
. 6 to 1. 2 
0. 5 by i. 7 
• 5 by i. 3 
. 5 by 1. 6 
. 7 by 1. 8 
. 5 by 1. 6 
■ S by 1. 7 
•5 by .9 
B . solanisaprus . 
B, melanoaenes . 
IIIA .. 
SE . 
IIP . . . . 
B. phytophthorus from Appel ... 
If the strain known as B. phytophthorus from Appel be omitted, it 
will be seen that, while there are minor variations with different stains, 
the three organisms from Maine run a little larger than those previously 
named and described. Of these, IIIA is slightly larger than the other 
two. Of the remaining three, while B. solanisaprus is plainly somewhat 
smaller, on the average this difference is very slight. Taken as a whole 
it seems difficult to separate the six different strains on the basis of 
the morphological characters. It is true that the measurements given 
differ somewhat from those previously recorded for the described organ¬ 
isms. The writer is not in position to say which are the more accurate, 
but this does not appear to him to be the important point under .con¬ 
sideration. What is given here is the relative measurements from 
stained preparations of the different organisms, made under as nearly 
uniform conditions as possible, and measured by the same individual, 
using the same apparatus for all. 
CULTURAL FEATURES 
Agar strokes. —On agar slants the growth characters of B . atrosep - 
ticus , B. solanisaprus , B. melanogenes , IIIA, SE, and IIP were identical 
in every respect except as noted below. The growth was moderate, 
filiform, with a slight tendency to produce pseudopod-like branches on 
the surface, if the latter was slightly moist, or such branches might grow 
up from the bottom of the slant from the condensation water. Eleva¬ 
tion flat to slightly raised, luster glistening, topography smooth. Slightly 
but distinctly bluish opalescent to transmitted light (a smear on the 
surface of slants with a loop would produce a decidedly opalescent 
growth). Color pearly white, odor absent, consistency butyrous, slightly 
viscid in the case of B . solanisaprus and B. melanogenes . No discolora¬ 
tion of the medium was observed in any of the cultures of the organisms 
named above. 
B. phytophthorus from Appel differed from the above in that the growth, 
though moderate, was spreading and very finely plumose, giving a char¬ 
acteristic appearance under a low-powered hand lens. B . phytophthorus 
67906°—17-4 
