874 
Journal of Agricultural Research voi. xxiv. No. lo 
(Table III). At a concentration of Ph 2.66 no maceration occurred. At 
the other concentrations about 48 hours were required for the cells to 
completely lose their coherence. There is therefore a degree of acidity 
such that the acid has no action on the middle lamellae in 48 hours 
(Ph 2.66, Table III). At a Ph of 2.59 little maceration took place in 48 
hours. In the remaining solutions (Table III) the acidity is about suffi¬ 
cient to dissolve the middle lamellae in 48 hours. At Ph i-7b maceration 
is complete in 24 hours and at i.01 in 5 hours. Similar data are shown 
in Table IV. 
The data presented in Tables V and VI were obtained by growing R, 
tritici on sweet-potato decoction adjusted to the different Ph values. 
These show that the decoction does not become as acid as Czapek’s solu¬ 
tion. No growth occurred in Ph 127 and 2.03 (Table VI), but at all other 
concentrations about the same amount of mycelium was produced. The 
hydrogen-ion concentration of the solutions when there was growth was 
considerably increased; however, in no case was the increase as great as that 
found in Czapek’s solution. At the two higher concentrations the macer¬ 
ation produced was doubtless due to the action of the acid, since in one 
case (Ph 1.27, Table V), although there was no mycelium produced, co¬ 
herence of the cells was lost in 2 hours, and in another case (Ph 2.10, 
Table V) in 7 to 24 hours. In all the other concentrations the middle 
lamellae were completely destroyed in from 2 to 2^ hours in the unsteamed 
solutions. In the steamed solution there was practically no maceration 
in 48 hours. 
The conclusions to be drawn from these data are, first, that pectinase 
is not produced in Czapek’s nutrient solution at any hydrogen-ion concen¬ 
tration tried and, second, that its production in sweet-potato decoction 
is not interfered with when the hydrogen-ion concentration is not so high 
as to prevent growth. In other words, pectinase is produced by R. 
tritici when growing in sweet-potato decoction at any hydrogen-ion con¬ 
centration that will permit its growth. Pectinase was also present in the 
mycelium. 
The amount of sugar present in the control (not inoculated) and the 
inoculated solutions was determined for Czapek’s solution only. At the 
higher hydrogen-ion concentrations no fungous growth took place and 
no sugar was used. As a matter of fact, there appears to be a slight 
increase in the amount of sugar present in the controls over that in the 
inoculated solutions, probably due to some concentration of the sugars 
as a result of evaporation. A measurable amount of sugar was con¬ 
sumed by the fungus at all other hydrogen-ion concentrations, the 
larger amount being at the higher Ph values. It will be noted that 
the amounts of sugar consumed at the lower hydrogen-ion concentrations 
are proportionately greater than in the less alkaline solutions. This is 
also true in the controls. No doubt this variation may be accounted for, 
at least in part, by the reaction between the sugar and alkali. The 
largest amount of mycelium was produced at the lower hydrogen-ion 
concentrations. 
An examination of Tables III and IV shows that in Czapek^s nutrient 
solution the amount of mycelium produced increases with the decrease 
in hydrogen-ion concentration, varying from 0.0283 gm. to 0.1780 gm. 
(Table III) and from 0.0340 to 0.1734 gm. (Table IV). No mycelium 
was produced at the highest hydrogen-ion concentration. In experi¬ 
ment 3, the dry weight of the mycelium was not determined, but in 
experiment 4 (Table VI) there was a more or less gradual increase in dry 
