io8 
Journal of Agricultural Research 
Vol. VIII, No. 3 
change to stratiform, and progresses very slowly from that time on. 
These variations were common to all of the pathogens and were not 
confined to any one of the series. No change of color or fluorescence was 
observed. The liquefied medium is quite turbid at first, and a copious 
flocculent or granular, whitish deposit settles out into the bottom of the 
funnel. 
Of the two cultures received as B . phytophthorus , that from Appel did 
not liquefy gelatin and that from Schuster produced first a crateriform 
and then a stratiform liquefaction of only the upper portion of the 
medium, which was browned. 
Nutrient broth. —In neutral nutrient broth (10 c. c. inoculated with 
a 2-mm. loop of young broth culture) the clouding in the case of B . 
airosepticus , B . solanisaprus , B . melanogenes , IIIA, SE, and IIP is very 
rapid. It is apparent in 13 to 16 hours at 20° C., varying somewhat with 
different strains, very evident in 18 hours, and is quite marked in from 
24 to 48 hours. Eater moderate to strong, persistent, the fluid being 
frequently turbid in old cultures. Usually a very slight ring may be 
observed in young cultures, and occasionally a very slight, granular 
pellicle is formed during the first few days of growth which readily breaks 
up and falls to the bottom if the tube is handled or even slightly jarred. 
The sediment is compact, scant, granular, and dirty white. No odor 
was observed and' no discoloration of the medium. As a rule, a very 
slight viscidity in both sediment and liquid was noted in the case of B . 
solanisaprus and B ., melanogenes . Otherwise the six above-named 
organisms were exactly identical in respect to observed characters upon 
bouillon. 
The organism received from Appel as B. phytophthorus differed from 
the above in that with it the sediment is very adhesive. While it was not 
strictly viscid it resisted pulling apart with the needle and then appeared 
very stringy. There was no evidence of viscidity of the medium itself 
in cultures of this organism. .The organism received from Schuster as 
B . phytophthorus differed from all the others in that in old cultures the 
medium was distinctly browned. While the sediment was dirty white 
it was rather more abundant, and appeared more stringy and viscid than 
was th£ case of the other culture carried under this name. 
Growth in potato broth. —The potato broth used was made as 
follows: Sound, fresh, recently harvested potato tubers were used and 
after peeling and washing, 500 gm. were grated directly into 1000 c. c. 
of distilled water. This potato pulp and water was heated for one hour 
a.t a temperature of 55 0 C. and filtered first through cotton and then 
through filter paper to remove the starch and pulp. The filtrate was then 
placed in the steamer for 40 minutes at 99 0 to ioo 0 C., and again filtered 
through paper. Titration showed the natural acidity to be equivalent 
to -f10 Fuller’s scale and this was not changed. The medium was then 
tubed and sterilized by fractional steaming—15 minutes at 99 0 to ioo° C. 
