July 21, 1923 
Hydrogen-Ion Changes 
163 
an unqualified answer to this question can not be given. All evidence 
along this line must be based on the action which the enzyms in solution 
have on cellular structures. It is a well-known fact that in the decay of 
certain vegetables and fruits by such organisms as Rhizopus and Botrytis 
the cells lose their coherence, probably as the result of the action of an 
enzym. It is also well known that some fungi will produce such an ac¬ 
tion on some hosts and not on others, which suggests the possibility that 
the macerating principle produced by one fungus may be quite different 
from that produced by another. 
SUMMARY 
(1) The influence exercised by the growth of 11 different species of 
Rhizopus on the acidity of the substrate (Czapek’s nutrient solution) 
was studied. It was found that two species {Rhizopus nigricans and 
R. microsporus) make the solution less acid. All the other species make 
it more acid. 
(2) The expressed juice from sweet potatoes decayed by R. tritici was 
found to be more acid than that from potatoes decayed by R. nigricans. 
Raw sweet-potato disks suspended in the juice of potatoes decayed by 
R. tritici were macerated in a shorter time than those immersed in juice 
from potatoes decayed with R. nigricans. If the juice in both cases is 
brought to the same hydrogen-ion concentration, the disks are macerated 
in the same length of time. 
(3) Tight exercised very little influence on the production of pectinase. 
(4) Changes in hydrogen-ion concentration of the substrate induced 
by Botrytis cinerea were studied for several different media. The results 
show that the hydrogen-ion concentration of some substrates is increased, 
while that of others is decreased. 
(5) Botrytis cinerea , although not normally a sweet potato storage-rot 
organism, produces a small amount of pectinase capable of dissolving 
the middle lamellae of raw sweet-potato disks when grown in artificial 
cultures. 
LITERATURE CITED 
(1) Bary, Anton de. 
18S6. UEBER ElNIGER sclerotinien und sclerotienkrankheiten. 
In Bot. Ztg., Jahrg. 44, p. 377-387, 393“403, 409-426, 433-442, 449“462, 
465-474. 
(2) Brown, William. 
1915. STUDIES IN THE PHYSIOLOGY OR PARASITISM. I. THE ACTION OR BOTRY¬ 
TIS cinerea. In Ann. Bot., v. 29, p. 313-348. References, p. 348. 
(3) Currie, J. N. 
1917. THE CITRIC ACID RERMENTATION OR ASPERGILLUS NIGER. In Jour. Biol. 
Chem., v. 31, p. 15-37, 2 fig-> 2 pi- 
(4) Harter, L. L., and Weimer, J. L. 
1921. A COMPARISON OR THE PECTINASE PRODUCED BY DIRRERENT SPECIES OR 
rhizopus. In Jour. Agr. Research, v. 22, p. 371-377, 2 fig. 
(5) Kissling, E. 
1889. zur biologiE DER botrytis cinEREa. In Hedwigia, Bd. 28, p. 227-256. 
(6) Larar, Franz. 
1910. technical mycology. Transl. by Charles T. C. Salter, v. 2, pt. 2. 
London. 
(7) LendnER, Alfred. 
1897. DES INRLUENCES COMBINEES DE LA LUMlERB ET DU SUBSTRATUM SUR 
LE dEvELoppement des champignons. In Ann. Sei. Nat. Bot., ser. 
8, tome 3, p. 1-64, 7 fig. Bibliographic, p. 64. 
(8) Levin, Ezra. 
1916. LIGHT AND PYCNIDIA RORMATlON IN THE SPHAEROPSIDALES. In 17th 
Ann. Rpt. Mich. Acad. Sci., 1915, p. 134-135. 
