Jan, is, 1917 
Blackleg Disease of Potato 
US 
except B. phytophthorus from Appel when so tested at once showed a deep- 
blue color reaction, indicating the presence of nitrites. No such color 
appeared in the uninoculated check tubes of the same medium tested 
at the same time. 
From what is said in the preceding section it might be inferred that 
B. phytophthorus from Schuster is apparently able to reduce nitrates to 
nitrites and then to ammonia. However, it should be remembered that 
the nitrate broth used contained a small quantity of peptone, and it has 
been shown that the organism is able to produce ammonia from peptone. 
Doubtless this was the source of the ammonia reaction in the nitrate 
broth. 
Indol production. —Cultures of B. atrosepticus , B. sotanisaprus , 
B . melanogenes , the three Maine organisms and of the one received from 
Schuster as B. phytophthorus gave a positive reaction to the indol test. 
That received from Appel as B. phytophthorus and the check tubes always 
gave a negative reaction. The pink color, while well defined, and some¬ 
times in old cultures being quite marked, was very much less than that 
produced by B. coli> which was tested at the same time for comparison. 
In the case of the positive-reacting organisms the color was very slight or 
absent in cultures four to seven days old and was most marked in cul¬ 
tures two months old or more. Therefore, indol production where it 
occurred would be classed as being feeble to moderate. 
Toleration oe acids. —In the present studies only hydrochloric 
acid has been tested. Normal hydrochloric acid was added to meat- 
extract broth which in the beginning was neutral to phenolphthalein, 
in sufficient quantities to make it +10, +20, +30, +40, and +50 
Fuller's scale. 
In from 12 to 18 hours all of the organisms showed equally good growth 
in the check tubes of neutral broth. At +10 the amount of clouding 
was nearly equal to that produced in the checks. At this time there was 
a marked falling off in the clouding at +20 as compared with the check 
tubes, and no growth had appeared in the presence of the larger amounts 
of acid. 
At 48 hours and later there was no change in the relative amounts of 
cloudiness exhibited by the different organisms, except that cultures of 
B. phytophthorus from Appel were slightly less cloudy and B. phytoph¬ 
thorus from Schuster were slightly more cloudy at + 20 than those of £. 
atrosepticus , B. solanisaprus , B. melanogenes , IIIA, SF, and IIP. The 
latter were all alike in their behavior toward hydrochloric add. None 
of the various organisms produced any growth at + 30 or beyond. 
Toleration oe sodium hydrates. —Cultures of all of the organisms 
were made in meat-extract bouillon, neutral to phenolphthalein, in com¬ 
parison with the same medium made —10, —20, —30, —40, and —50 
Fuller's scale with normal sodium-hydrate solution. 
