1014 
Journal of Agricultural Research 
Vol. XXX, No. H 
quired to neutralize them, indicate 
that the organisms reacted amphoteric 
at hydrogen-ion concentrations be¬ 
tween P H of 3.0 and 5.0. It means, in 
other words, that the “isometabolic 
point,” (11) or the initial Ph value of the 
culture solution which is not altered 
by the reactions of the organism during 
the utilization or assimilation of dex¬ 
trose, lies between the Ph values of 3.0 
and 5.0. The phenomenon of varia¬ 
tion in the biochemical behavior of 
different species, during the assimila¬ 
tion of different nutrient substances, 
may serve as a character for the 
differentiation of groups and possibly 
of species of Fusarium. It is possible, 
therefore, when one considers (a) the 
behavior of the different organisms at 
hydrogen-ion concentrations between 
P H of 3.0, 4.0, and 5.0, ( b ) the color 
and intensity of the pigment, and (c) 
the diffusibility of the pigment, to 
segregate the Fusaria given in Table I 
into more or less congenial groups. 
For instance, F. cromyophthoron, F. 
redolens and F. malli, may be put in 
one group; F. radicicola and F. martii, 
in another; F. culmorum and, possibly, 
F. moniliforme, in another, and all the 
remaining organisms in one more 
group. 
The behavior of F. cromyophthoron 
in onion decoction does not differ from 
that in dextrose solutions, except in the 
position of the P H value of the “isome¬ 
tabolic point” which lies near or at 
P H of 5.0, in onion decoction (Table II). 
Table II.— Color and intensity of pig¬ 
ment produced by Fusarium cromy¬ 
ophthoron in onion decoction at differ¬ 
ent hydrogen-ion concentrations and 
volume of adjusting reagents required 
to maintain the Ph value constant dur¬ 
ing the growth of the organism 
Initial 
Adjusting reagents 
P H value 
Color of pigment 
of 
culture 
HC1 
Na OH 
3.0. 
20 
0 
Phlox purple. 
4.0_ 
9 
0 
Van Dyke red. 
5.0.- 
0 | 
1 
Orange pink. 
Colorless. 
6.0_ 
0 ! 
15 
7.0_ 
0 
60 
Do. 
7. 6_ 
0, 
95 
Do. 
NONADJUSTED CULTURES 
These cultures are concerned with 
the study of the development of pig¬ 
ment by Fusaria in dextrose solu¬ 
tions whose initial hydrogen-ion con¬ 
centration was not maintained con¬ 
stant by the introduction of volumes 
of adjusting reagents. The hydrogen- 
ion concentration of the culture solu¬ 
tion which influences the development 
of pigment in these cultures is not a 
constant factor but a variable one. 
This can easily be explained when one 
considers that the hydrogen-ion con¬ 
centration of these cultures is not 
maintained constant by the addition 
of adjusting reagents, but is subject to 
the reactions of the metabolic prod¬ 
ucts of the organism. The pigment, 
therefore, which is developed under 
these conditions, is subject to the 
changes which are produced in the 
hydrogen-ion concentration of the cul¬ 
ture solution by the reactions of the 
organism with the substratum. 
The culture media employed for these 
studies contained 2 per cent agar-agar. 
They were solid media, prepared in the 
manner mentioned previously. The or¬ 
ganisms were grown in Petri-dish cul¬ 
tures, containing 20 c. c. of the media. 
The observations on the develop¬ 
ment of pigment were made during 
the first 12 days’ growth of the organ¬ 
ism on the above culture media, and 
are recorded in Table III. 
Table III.— Color of the pigment 
produced by different species of Fusa¬ 
rium at different initial hydrogen-4on 
concentrations of dextrose-agar cultures, 
during a 10-day growth 
In¬ 
Organism 
itial 
Ph 
Color of pigment 
Fusarium cromyoph¬ 
thoron Sid_ 
4.0 
Cinnamon pink. 
Cinnamon. 
Do. 
5.0 
Do. 
6.0 
Cinnamon purple. 
Do. 
7.0 
Vinaceous purple. 
Do. 
7.5 
Do. 
F . redolens Sher. 
4.0 
Cinnamon pink. 
Do. 
5.0 
Cinnamon. 
Do..... 
6.0 
Cinnamon purple. 
Do. 
7.0 
Vinaceous purple. 
Do-. 
7.5 
Do. 
F. malli Taub. 
4.0 
Cinnamon pink. 
Do. 
5.0 
Cinnamon. 
Do. 
6.0 
Cinnamon purple 
Do. 
7.0 
Vinaceous purple. 
Do. 
7.5 
Do. 
F.lntulatum Sher. 
4.0 
Light vinaceous 
pink. 
Do. 
5.0 
Do. 
Do. 
6.0 
Shrimp pink. 
Do. 
7.0 
Do. 
Do. 
7.5 
Shrimp, pale. 
F. oxysporum Scht_ 
! 4.0 
Light vinaceous 
pink. 
Do. 
5.0 
Do. 
Do. 
1 6.0 
Shrimp pink. 
Do. 
’ 7.0 
Do. 
Do. 
1 7.5 
Shrimp, pale 
F. oxyporum var. 
| 4.0 
Light vinaceous 
Sher. 
1 5.0 
pink. 
Do. 
do::::::::;::::;: 
6.0 
Shrimp pink. 
Do. 
7.0 
Do. 
Do. 
7.5 
Shrimp, pale. 
