220 
Journal of Agricultural Research 
Vol. XXI, No. 4 
ECONOMIC COEFFICIENT 
Pfeffer (17) and Kunstmann ( 14 ) have termed the numerical relation 
between the sugar consumed and the dry weight of the substance formed 
the “economic coefficient.” According to Jost (n) the theoretical 
minimum value of the coefficient is about but m reality it has been 
found to be higher than unity. Kunstmann found in working princi¬ 
pally with Aspergillus niger that it varied from 1.13 to 3.88 in parallel 
experiments in a 5 per cent solution of cane sugar. Ono (16), on the 
other hand, obtained values as high as 6.1. 
The results obtained by the writers are shown in column 10 of Table 
I. It will be seen that the economic values for Fusarium acuminatum 
and Mucor racemosus are very much higher than any of those given by 
Kunstmann and Ono, being 17.11 and 22.86, respectively. The five 
other organisms are fairly consistent in the amount of sugar required to 
produce 1 gm. of dry substance, all of which, however, are equal to or 
higher than the maximum given by Kunstmann. In view of these facts, 
it is quite evident that fungi in general can in no sense be regarded as 
economic users of sugar. In none of the writers’ experiments or in those 
of Kunstmann and Ono has the minimum value of the economic 
coefficient fallen below unity. 
From the data at hand it is evident that no sweeping generalizations 
can be made for all fungi. Ono showed that the addition of a small 
amount of zinc sulphate reduced the “economic coefficient,” and Jost 
points out that the coefficient increases with the progressive develop¬ 
ment of the fungus and with an elevation of the temperature. Since the 
progressive development of the fungus influences the coefficient, the ele¬ 
ment of time would have an important bearing on the results. Although 
all of these experiments were carried out at the same temperature (29°C.), 
no doubt the fungi studied did not respond to heat in a similar manner. 
RESPIRATORY QUOTIENT 
The dry weight of fungus material produced for each gram of C0 2 
given off is in all cases considerably less than unity (Table I, column 
11). To contrast the extremes, Rhizopus tritici formed about four times 
as much dry material as Mucor racemosus. Kunstmann in all his ex¬ 
periments obtained a much higher numerical value of the respiratory 
quotient with Aspergillus niger in a 5 per cent cane sugar solution. In 
a few cases considerably more than 1 gm. of dry weight was produced 
for each gram of C 0 2 given off. Kunstmann’s results are not in every 
respect comparable, since he used different temperatures in different 
experiments. The higher temperatures for the most part appeared to 
lower the value of the “ respiratory quotient.” However, it may be con¬ 
cluded that in general under experimental conditions considerably more 
than 1 gm. of C0 2 is given off for each gram of fungus material formed. 
