SECRETION OF DIASTASE BY PENICILLIUM CAMEMBERTII 255 
and diastase secretion. This, however, is not the case, as is shown by 
the following experiment, in which a different solution^ was employed 
and the rate of digestion of starch was noted both in the presence and 
in the absence of potassium. The time required for the digestion of 
the starch in 50 cc. of the medium containing no K nor Na, and of the 
starch in 50 cc. of the same medium containing KH2PO4 or NaH2P04 
as indicated in Table IX, was determined by the method of Katz. 
Triplicate cultures were grown in the dark at room temperature, and 
the dry weight of the mycelium was determined as each culture showed 
complete disappearance of the starch. 
Table IX 
Time for Digestion Dry Weight of My- 
50 Cc. of Medium Plus (Days) celium (Mg.) 
M/io KH2PO4 
6 
14.7 
M/ioo KH2PO4 
6 
II. I 
M/iooo KH2PO4 
4 
6.4 
M/io,ooo KH2PO4 
6 
10.6 
M/ioo,ooo KH2PO4 
7 
6.6 
No phosphate 
8 
5-1 
M/io NaH2P04 
9 
9.6 
M/ioo NaH2P04 
8 
54 
M/io,ooo NaH2P04 
6 
6.7 
M/io,ooo NaH2P04 
7 
6.4 
.4 percent starch onlv 
II 
Weight not 
It can be noted from the number of days required for complete 
digestion given in Table IX that a deficiency of potassium has little 
effect on the time required for digestion. In the medium used here 
it requires Penicillium camembertii but 8 days to digest 0.2 g. of 
starch in a deficiency of both potassium and phosphorus, which differs 
by but one or two days from the time necessary for complete digestion 
when both these elements are present in abundance. It would there- 
fore appear that the long period of digestion in the minus potassium 
cultures of Table IX is due not to the lack of potassium, but to some 
other cause. This cause is apparently an inhibitive action of the 
^ The nutritive solution used was composed of 
Ca(N03)2 0.236 g. (M/ioo) 
MgS04 0.0246 g. (M/iooo) 
FeCls Trace 
Starch. , 0.4 percent 
Water 100 cc. 
KH2PO4 or NaH2P04 As indicated. 
