May i6,1921 Glucose as a Source of Carbon for Storage-Rot Fungi 201 
fungi. Mucor racemosus , requiring 28.88 gm., stands at one extreme 
and Sclerotium bataticola , requiring 5.02 gm., at the other. Fusarium 
acuminatum , Diplodia tubericola , and Rhizopus tritici required 17.52, 
8.78, and 17.67 gm., respectively. Pfeffer (25) and Kunstman (18) have 
termed the numerical relation between the sugar consumed and the dry 
weight of the substance formed the “economic coefficient.” The mini¬ 
mum amount of sugar required to produce 1 gm. of dry weight shows 
likewise great variation. A comparison of F. acuminatum and M. 
racemosus , the two extremes, shows that the “economic coefficient” of 
the former is about 4.4 times greater than that of the latter. These 
differences correspond fairly well with results obtained by Kunstmann 
working with Aspergillus niger and Penicillium glaucum , who found 
it to vary from 1.13 to 3.88, while Ono (24) obtained a value as high as 
6.1 when working with A. niger . 
These results indicate that the coefficient cannot be looked upon as in 
any way constant. It differs with different fungi grown under identical 
conditions. There may be several factors which influence the results. 
According to Jost (17), the coefficient increased with the progressive 
development of the fungus and with the elevation of the temperature. 
Toxic substances likewise were shown by Ono to increase the coefficient 
in Aspergillus. Since these organisms were all grown at the same 
temperature, it would be largely eliminated as a controlling factor. On 
the other hand, some of the chemicals or impurities composing the 
nutrient medium might have a toxic action on some of the organisms. 
Furthermore, it is likely that the different fungi vary greatly in their 
ability to form other substances, such as alcohol, organic acids, etc., 
which might be toxic or inhibit normal growth. In some cases it has 
been shown that alcohol is actually produced. That all organisms are 
not equally influenced by these changes is probably true. In the more 
resistant forms growth would continue for a longer time and thus possi¬ 
bly produce a greater amount of fungal material per unit volume of sugar. 
What changes the fungus actually brings about must remain unknown 
until chemical methods permit of the quantitative determinations of the 
different products and materials formed. 
HYDROGEN-ION CONCENTRATIONS 
The hydrogen-ion concentrations express in P H values were determined 
from representative samples of all the solutions. These are recorded in 
Table VII. 
