1016 
Journal of Agricultural Research 
Vol. XXX. No. 11 
increased it again toward the same 
point, were responsible for the forma¬ 
tion of the favorable hvdrogen-ion 
concentration for the development of 
pigment. Another interesting phe¬ 
nomenon, in this connection, is the de¬ 
velopment of different colors of the 
same pigment at different hydrogen-ion 
concentrations. At hvdrogen-ion con¬ 
centrations higher or near that of the 
isometabolic point the majority of the 
pigments have a reddish-pink color. 
At hydrogen-ion concentrations, how¬ 
ever, lower than that of the isometab¬ 
olic point, the same pigments, instead 
of the reddish-pink color, have a purple, 
blue, yellow, or green color. 
The behavior of Fusarium cromyoph- 
thoron in dextrose solution and onion 
decoction at different hydrogen-ion 
concentrations (Tables IV and V) was 
practically similar to that observed 
in solid media; that is, pigment was 
produced at all the different initial 
hydrogen-ion concentrations between 
P H of 3.0 and 7.5. The slight varia¬ 
tion in the color of the pigment of the 
sporodochia of F. cromyophthoron 
(Table VI) is possibly due to the in¬ 
herent hydrogen-ion concentration or 
to the difference in the amounts of car¬ 
bohydrates and proteins contained in 
the different tissues. If one takes into 
account the chemical composition of 
the tissues in its relation to the color 
produced in the sporodochia of F. 
cromyophthoron , one finds, according to 
Wehmer {12), that the pale ochraceous 
salmon color is associated with tissues 
rich in available carbohydrates and the 
pale ochraceous buff color with those 
poor in available carbohydrates but 
somewhat rich in available proteins. 
MOVEMENT OF THE REACTIONS IN 
SOLID MEDIA 
These studies are concerned with the 
movement of the reactions, particu¬ 
larly those of the hvdrogen-ion con¬ 
centration produced by the different 
organisms, in solid media. 
Dextrose agar media were used for 
the purpose. They were prepared in 
the manner mentioned in a preceding 
paragraph. The culture media were 
tubed in 20 c. c. portions and sensitized 
with 10 drops of either one of the indi¬ 
cators used for the determination of 
different hydrogen-ion concentrations, 
namely, brom phenol blue, methyl red, 
and brom thymol blue. Inoculations 
were made with pure cultures of the 
different Fusaria in slanted media; 
and the nature, extent, and movement 
of the changes in the initial hvdrogen- 
ion concentration were examined daily. 
The initial hvdrogen-ion concentra¬ 
tion of the culture media at the time of 
the inoculation was P H of 5.0. This 
method was first adopted by Wolf (13) 
and was used in connection with the 
changes produced in the hydrogen-ion 
concentration by certain plant patho¬ 
genic bacteria. The changes in the 
hvdrogen-ion concentration were de¬ 
termined by the changes in the color of 
the particular indicator and are re¬ 
corded in Table VII. 
Table VII .—Changes produced on the 
color of the different indicators by the 
reactions of metabolic products of the 
different species of Fusarium on the hy¬ 
drogen-ion concentration of the culture 
media 
Organism 
Days 
of 
growth 
Determinations of the 
changes in the hydro¬ 
gen-ion concentration 
Methyl 
red 
Brom 
phenol 
blue 
Brom 
thymol 
blue 
Fusarium cro¬ 
myophthoron 
Sid 
! 4 
Ph 
5.0 
Ph 
Ph 
Do _ _ 
6 
3.9 
Do_ _ 
8 
4.5 
Do_ 
10 
6~8 
Do_ 
12 
7.2 
F. malli Taub_ 
4 
5.0 
Do 
6 
4.0 
Do 
8 
4.6 
Do_ 
10 
6.0 
Do_ 
12 
7.4 
F. lutulatum j 
Sher 
4 
5.0 
Do 
6 
4. 2 
Do 
8 
j 4.6 
Do _ 
10 
6.6 
Do_ 
12 
_ j_ 
7. 6 
F. oxysporum 
Scht _ 
4 
5.0 
Do. . _ 
6 
3. 8 
Do_ 
8 
4.2 
Do . _ 
10 
5.4 
Do . . 
12 
5.8 
F. oxysporum 
var. longious 
Sher 
4 
5.0 : 
; 
1 
Do. . . 
6 
4.0 j 
Do 
8 
4.4 | 
Do. 
10 
6.6 
Do 
12 
7.4 
F. oxysporum 
var. resupina- 
tum Sher 
4 
5.0 1 
Do 
0 
3. 8 
Do 
8 
4.2 
Do 
10 
6.8 
Do 
12 
7.6 
F. an g us t u m 
Sher 
4 
5.0 
! 
Do 
6 
3.6 i 
Do 
8 
4.4 
Do 
10 
6. 6 
Do 
12 
7. 6 
F. lonchecer as 
Sid 
4 
5.0 
Do 
0 
3. 6 
Do 
8 
4.4 
Do 
10 
6. 6 
Do_ 
12 
7. 6 
