Journal of Agricultural Research 
Vol. XXX, No. 10 
hours. None was secreted on prune or 
potato decoction or when the fungus 
was grown on beef bouillon or on 
Czapek’s, Pfeffer’s, or Richard’s solu¬ 
tion. These latter media have con¬ 
sistently failed to stimulate the pro¬ 
duction of the enzyme. This result is 
not so surprising, since the synthetic 
media are not supposed to contain any 
of the pectic compounds, which have 
been found to exercise a more or less 
regulatory influence on the secretion 
of pectinase. 
Eight days after inoculation the re¬ 
maining seven flasks were taken off. 
The mycelium from the flasks of the 
same substrate was brought together 
and used for dry-weight determinations. 
The total dry weight of the mycelium 
from these seven flasks proved to be as 
follows (average two experiments): 
Prune decoction, 0.2632 gm., sweet- 
potato decoction, 0.5668 gm.; carrot 
decoction,0.3224gm.; potato decoction, 
0.3513 gm.; turnip decoction, 0.4845gm.; 
string-bean decoction, 0.3684 gm.; beef 
bouillon, 0.2502 gm.; Czapek’s solution, 
0.4253 gm.; Pfeffer’s solution, 0.3600 
gm.; Richard’s solution, 0.4476 gm. 
These data show that a fair growth of 
mycelium was produced in all the culture 
media used. However, there seems to 
be very little if any correlation between 
the amount of dry material and the 
production of pectinase. The smallest 
amount of dry material was produced 
on prune decoction and in beef bouillon, 
the media in which pectinase was not 
secreted. On the other hand, Richard’s 
and Czapek’s solutions, in which pecti¬ 
nase is not secreted, produced a con¬ 
siderable quantity of dry matter. 
The hydrogen-ion determinations 
were made of the used and unused 
solutions at the end of the growth 
period on the same day the solu¬ 
tions were removed from the incubator. 
The control flasks, which were wrapped 
over the top with oiled paper to prevent 
evaporation, were kept in the incubator 
beside the inoculated ones. When re¬ 
quired for hydrogen-ion determinations 
the contents of the different flasks of 
each medium were collected into one 
compound sample. The hvdrogen-ion 
concentration of all the vegetable de¬ 
coctions, except prune, also that of beef 
bouillon, is decreased by an 8-day growth 
of Mucor racemosus, but that of Cza¬ 
pek’s, Pfeffer’s, and Richard’s solutions 
is increased or left practically un¬ 
changed (Table I). 
Diploma tubericola. —The same 
media were used in studying this or¬ 
ganism as were used with Mucor race¬ 
mosus. No pectinase was produced by 
Diplodia tubericola on any of the media 
used, and in view of that fact none of 
these data will be given. 
Table I.— Hydrogen-ion concentration 
of the controls and used solutions after 
8 days’ growth of Mucor racemosus. 
Average of two experiments 
Solution 
Control 
(Ph) 
Inocu¬ 
lated 
solution 
(Ph) 
Prune decoction ... 
1 795 
3.645 
Sweet-potato decoction. 
5.075 
7.28 
Potato decoction” I . 
o! 525 
7. 99 
Turnip decoction.. 
String-bean decoction. 
Beef bouillon. ... 
4. 625 
7.18 
7.455 
7.58 
8.445 
Czapek’s solution. 
5.08 
3. 71 
3.485 
3.76 
Richard’s solution. 
3. 595 
3.60 
For the determination of the influ¬ 
ence of the medium on dry-weight pro¬ 
duction and hydrogen-ion concentra¬ 
tion the cultures were incubated for 10 
days at 30° C. The same methods of 
procedure for the determination of dry 
weight of the mycelium and of the hy¬ 
drogen-ion concentration were followed 
as with Mucor racemosus. The results 
of these total dry-weight tests (aver¬ 
age of two experiments) are as follows: 
Prune decoction, 3.925 gm.; sweet-po¬ 
tato decoction, 0.7200 gm.; carrot de¬ 
coction, 1.4498 gm.; potato decoction, 
0.4232 gm.; turnip decoction, 1.9966 
gm.; string-bean decoction, 0.8683 gm.; 
beef bouillon, 0.9886 gm.; Czapek’s so¬ 
lution, 1.9882 gm.; Pfeffer’s solution, 
2.4475 gm.; Richard’s solution, 1.0316 
gm. 
The amount of dry matter produced 
by Diplodia tubericola varied in the 
different media. The largest amount 
of dry material was produced in prune 
decoction, in which Mucor racemosus 
made a rather small growth. These 
data show that a medium which is well 
suited for the growth of one organism 
may not necessarily be suited for the 
growth of another. 
To ascertain the hydrogen-ion con¬ 
centration of the solutions, the contents 
of all the flasks of the same medium 
were collected into one compound 
sample and the P H value determined as 
for Mucor racemosus. The results are 
given in Table II. 
From Table II it is seen that Diplo¬ 
dia tubericola decreased the hydrogen- 
ion concentration of all the vegetable 
decoctions and of beef bouillon. The 
hydrogen-ion concentration of the three 
synthetic media (Pfeffer’s, Richard’s, 
and Czapek’s) was increased. 
