1018 
Journal of Agricultural Research 
Vol. XXX, No. 11 
EXPLANATION OF RESULTS 
The results given in Table VIII in¬ 
dicate that the pigment, produced at 
P H of 4.0 and 5.0 by certain Fusarium 
species, if brought in contact with free 
hydroxyl ions, changes color from red¬ 
dish pink to blue, green, lilac, or pur¬ 
ple. Therefore the blue, green, and 
purple colors of the pigments of certain 
Fusarium species, produced at P H of 
7.0 and 7.5, were due to the influence 
of the hydroxyl ions of the culture 
media. It becomes evident, from a 
consideration of the results obtained 
in the different studies, that the organ¬ 
ism or organisms produce the chromo¬ 
gens necessary for the development of 
pigment at hydrogen-ion concentra¬ 
tions between P H of 3.5 and 5.5 and 
that the different colors which are 
formed from the chromogens later on 
depend on the hydrogen-ion concen¬ 
tration of the culture media. The 
mechanism by which these organisms 
bring about the appropriate reactions 
in the culture media for the develop¬ 
ment of chromogens and the formation 
of pigment of different colors is dis¬ 
cussed to a certain extent in the pre¬ 
ceding pages and more extensively in a 
different publication of the writer (11). 
GENERAL DISCUSSION 
The pigments produced by Fusaria 
belong possibly to the same class of 
pigments which are produced from 
chromogens named by Palladin (6) 
“respiration chromogens.” According 
to the same author, these chromogens 
are glucosides soluble in water and upon 
the addition of peroxidase and hydro¬ 
gen peroxide produce red (rarely lilac 
or violet) color which might change 
with further oxidation to a dark violet 
or black. Rupe (9) found that an alka¬ 
line solution of these chromogens ab¬ 
sorbs oxygen very actively, and Combes 
(3) found that the transformation of 
the chromogen into the pigment is ac¬ 
companied by increased respiratory 
activity. Palladin and L’vov (7) are 
of the opinion that these chromogens 
serve as acceptors of hydrogen. More¬ 
over, they state that they were able to 
retard the process of alcoholic fermen¬ 
tation by employing the respiration 
pigment of the white beet to remove 
the active hydrogen as it was formed. 
The pigments produced by Fusaria 
and those attributed by Palladin to 
respiration chromogens have certain 
reactions in common. Both are formed 
from chromogens during a very ac¬ 
tive respiration, absorb oxygen very 
rapidly in alkaline solutions; and are 
red or pink in acid solutions, and violet, 
purple, or blue in alkaline solutions. 
The series of reactions which initiate 
the development of pigment, during 
the assimilation of certain nutrient 
substances by Fusaria, are possibly 
produced as follows: The organisms, 
in culture media whose hydrogen-ion 
concentration is not appropriate for the 
development of chromogens, may or 
may not change the initial reaction of 
the culture media either by increasing 
or decreasing the hydrogen-ion con¬ 
centration with their metabolic prod¬ 
ucts. Then, if the hydrogen-ion con¬ 
centration of the surrounding culture 
solution is favorable for the develop¬ 
ment of chromogens, the organisms 
may produce these substances the color 
of which in acid solutions may be red, 
vinaceous, or pink, and in alkaline solu¬ 
tions violet, lilac, purple, blue, or 
green. 
Carbohydrates are essential for the 
development of pigments. The role 
which they play, in this respect, is not 
known exactly. They may supply the 
substances (glucose and organic acids) 
for the synthesis of glucosides, par¬ 
ticularly of the chromogen-glucoside, or 
the organic acids for the restoration of 
an hydrogen-ion concentration appro¬ 
priate for the development of chromo- 
gens. The development of chromogens 
is definitely controlled by the hydrogen- 
ion concentration of the surrounding 
solution. In dextrose solutions chro¬ 
mogens may be produced in cultures 
whose hydrogen-ion concentration is 
maintained constant by the addition of 
adjusting reagents at P H between 3.5 
and 5.5, but not above or below these 
values. 
Plate 1 shows the different colors of 
the pigment produced by Fusarium 
culmorum (W. Smith) Sacc. in solid 
media at different hydrogen-ion con¬ 
centrations. The colors from acid to 
alkali change from red to blue. The 
chromogen for the blue pigment at 
P H 7.5 and the purple at P H 7.0 was not 
produced at the above hydrogen-ion 
concentrations, but at such hydrogen- 
ion concentrations as were created by 
the organic acids produced by the 
organism during the utilization of 
dextrose. It is possible for the organ¬ 
ism, in solid media, to produce a local 
acidity or alkalinity, that is, a reaction 
which does not spread throughout the 
entire culture medium but is confined 
EXPLANATORY LEGEND FOR PLATE 1 
Fusarium culmorum, grown in solid media at different hydrogen-ion concentrations, namely, P H 4.0, 
5.0, 6.0, 7.0, and 7.5 
