July 21, 1923 
Hydrogen-Ion Changes 
161 
in the killing of the cells and another which brings about a softening of 
the tissues. The first is caused, he claims, by the acid, and the latter by 
one or more enzyms. Brown, on the other hand, was unable to demon¬ 
strate a killing action independent of that caused by the macerating 
principle and apparently leans to the view that the entire action, killing 
and macerating, is due to one and the same substance. Smith made 
no mention of the age of the mycelium which he used. Brown used 
mycelium only 1 or 2 days old, so that it is not likely that acids in any 
considerable amount were present in it. On the other hand, it is prob¬ 
able that an acid was produced in Smith’s cultures if he used mycelium 
several days or weeks old. The writers have shown that Rhizopus 
tritici does not produce an appreciable amount of acid until after about 
3 days. They are aware, however, that this is no indication of what 
Botrytis cinerea may do. 
The writers included a study of Botrytis cinerea in their investigations 
for three principal reasons. First, it has been studied by a number of 
investigators and shown to produce a substance capable of dissolving 
this middle lamellae of the cells of a number of different hosts; second, 
it has been shown by the writers that species of Rhizopus, which are not 
parasitic on the sweet potato, produce a weak macerating enzym when 
grown in culture. In other words, it was found that certain organisms 
which were not normally parasites on the sweet potato would produce 
an enzym or some substance when grown in culture which would act 
upon the middle lamellae. Whether or not this was a characteristic 
of all fungi was not known. Therefore, it was decided to make such a 
study of another organism which had already been shown to produce 
a cell-wall dissolving enzym and which was not a true parasite of the 
sweet potato. Third, it seemed necessary to determine whether an acid 
was produced which would cause a maceration of the cells, as the writers 
showed to be the case when Rhizopus tritici was grown on Czapek’s 
solution. 
Several different media were employed because the results of previous 
investigations showed that Rhizopus tritici , although it formed a pectinase 
when grown on sweet potato decoction, would not do so when cultivated 
on Czapek’s nutrient solution with glucose as a source of carbon. In 
order to partially eliminate the influence which the substrata might 
exert on the production of pectinase by Botrytis cinerea, six decoctions of 
vegetable origin, namely, string bean, prune, Irish potato, carrot, turnip, 
and sweet potato, three synthetic media, Czapek’s, Richard’s, and 
Pfeffer’s solutions, and beef bouillon were employed. The organisms 
were grown in 100 cc. Erlenmeyer flasks on 30 cc. of media. There were 
a number of flasks of each media. After inoculation the cultures were 
incubated in the dark at 28° C. for 7 days. At the end of the growth 
period the contents of all the flasks of one set were collected into one 
compound sample. The hydrogen-ion concentrations of the unin¬ 
oculated controls and the solutions on which the fungus had grown were 
then determined. The mycelium was saved from one set of experiments 
and its macerating power determined. On some of the solutions the 
growth was very poor and no hyphae were obtained. 
The results as expressed in Table V show that Botrytis cinerea increased 
the hydrogen-ion concentration in some solutions and decreased it in 
others. String bean and Irish potato decoctions were changed to a 
point on the alkaline side of neutrality, the action of the enzym being 
