June 1,1925 
H-ion Concentration and Pigment in Fusaria 
1019 
to the area covered by the colony of the 
organism, because the movement of the 
hydrogen ions or hydroxyl ions is very 
slow and the time required for their 
neutralization is relatively long. It is 
easy to see how, with the development 
of a local reaction, one with a Ph 
between 4.0 and 5.5 appropriate for 
the formation of chromogens is possible. 
The blue color of the pigment produced 
in alkaline cultures is due to oxidation 
which is accelerated by the presence of 
free hydroxyl ions in the surrounding 
solution. 
SUMMARY 
The development of pigment by 
Fusaria is mainly controlled by the 
hydrogen-ion concentration of the cul¬ 
ture media. 
Pigment was produced practically 
by all the different species employed in 
these studies in dextrose solutions at 
hydrogen-ion concentrations between 
P H 3.5 and 5.5, where the initial P H 
value was maintained constant by the 
addition of adjusting reagents. In 
cultures, however, whose hydrogen-ion 
concentration was not maintained con¬ 
stant, pigment was produced at P H 3.0, 
4.0, 5.0, 6.0, 7.0, and 7.5. 
The pigment may be of two kinds: 
Diffusible and nondiffusible, that is, 
pigment retained within the cell and 
pigment escaping through the plas¬ 
matic membrane and cell wall. 
The color which a pigment may take 
depends on the hydrogen-ion con¬ 
centration of the surrounding culture 
solution. 
The movement of the hydrogen ions 
and hydroxyl ions released by the re¬ 
action of the metabolic products of 
Fusaria through solid culture media is 
very slow. 
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