266 
Journal of Agricultural Research 
Vol. XXVIII, No. 3 
weeks with deep green fluorescence. Cultures kept one year on culture media 
liquefy gelatin very slowly. 
Milk. —Milk clears uniformly without coagulation, beginning about the seventh 
day. Cultures one month old are translucent and honey yellow. No crystals 
are formed at this time but an occasional culture held for three months has a few 
small masses of tyrosin crystals. The milk at this age is tawny yellow and 
translucent (Ridgway XV) 6 and the precipitate has become yellow. 
Litmus milk. —Litmus milk begins to blue on the third day from the top down¬ 
ward, then clears without coagulation. The cream rim when present is reddened. 
Reduction of the litmus begins in 10 days and is complete in 20 days. A copious 
white precipitate is formed. The blue color returns in 2 to 4 weeks. After 3 
months the milk is still blue and translucent but the precipitate has become 
yellow. 
Methylene blue milk. —Reduction begins on the second day and is com¬ 
plete in 3 to 5 days. No coagulation occurs. 
Cohn’s Solution. —Weak clouding is visible within 4 or 5 days and increases 
slowly for 5 or 6 weeks when the cultures are moderately clouded. After 3 months’ 
growth there is a small amount of white precipitate in the bottom of the tube 
with numerous small crystals. 
Uschinsky’s solution. —Within 24 hours a faint clouding may be seen in the 
upper part of the culture. By the second day a delicate pellicle has formed with 
blue-fluorescence just below it in the upper 2 or 3 mm. and by the fifth day 
clouding is heavy with a heavy pellicle and green fluorescence throughout. A 
heavy white precipitate is formed. 
Fermi’s solution. —There is prompt growth in Fermi’s solution with a beauti¬ 
ful blue fluorescence sometimes becoming green but more often remaining blue 
though held for several weeks. A heavy wrinkled pellicle is formed which does 
not fall readily on shaking, but clouding usually remains weak. Thumm 7 states 
that all of the colors produced by fluorescent bacteria are due to the same pig¬ 
ment, the blue becoming green with the production of alkali by the organism. 
The addition of dilute ammonia to blue cultures of Bad . delphinii in Fermi’s 
solution turned them a vivid green. Blue and green cultures were tested for 
relative acidity with the following results: 
Blue P H 6.5 or +41. 
Green P H 6.6 or +34. 
Nitrate reduction. —Nitrate is not reduced. Tests were made with nitrate 
bouillon cultures 5 days old and 10 days old in which moderate clouding had taken 
place, using the starch-iodin-sulphuric acid test. 
Nitrogen compounds. —The ability of the organism to obtain its nitrogen from 
various nitrogen compounds was tested in 1 per cent water solutions of the fol¬ 
lowing: peptone, asparagin, asparagin plus dextrose, ammonium citrate, am¬ 
monium tartrate and ammonium succinate. The results are shown in Table I. 
8 Ridgway, R. color standards and color nomenclature, pi. 15. Washington, D. O. 1912. 
7 Thumm, K. beitrage zur biologie der fluorescierenden bakterien. Arb. Bakt. Inst. Tech. 
Hochschule Karlsruhe 1: 291-377. 1897. Abstract in Smith, E. F. Bacteria in relation to plant diseases. 
1:238. 1905. 
