2l8 
Journal of Agricultural Research 
Vol. XXI, No. 4 
being only 0.058 and 0.044 respectively. Contrasted to these, 
Diplodia tubericola formed the most, namely, 0.258 gm., while Sclerotium 
bataticola and Rhizopus tritici formed 0.218 and 0.216 gin., respectively. 
COEFFICIENT OF RESPIRATION 
The number of grams of sugar reduced per gram of C0 2 evolved is 
shown in column 9. The differences in the case of several of the fungi 
are very large. Mucor racemosus is the most extravagant and Botrytis 
cinerea the most economical user of sugar when the comparison is made 
on the basis of C 0 2 produced, but it may be otherwise when the dry 
weight of fungus substance alone is considered. Four of the fungi 
studied require more and three less than 1 gm. of sugar to make 1 gm. 
of C 0 2 . Kunstinann ( 14) in working with Aspergillus niger v. Tieg. in 
a 5 per cent solution of cane sugar found a considerable variation in the 
results obtained from different experiments. In all cases, however, more 
than 1 gm. of sugar was required to form 1 gm. of C 0 2 , the variation 
ranging from 1.05 to 1.98. He further showed that a greater growth of 
the fungus was accompanied with an increase in respiration, as would be 
expected, and that the respiration became more rapid as the temperature 
rose. He showed, furthermore, that the concentration of the cane sugar 
in the nutrient solution influenced the rate of respiration, it being about 
1.5 times as rapid in a 30 as in a 5 per cent solution. In a solution made 
slightly acid with phosphoric acid (P 2 0 6 ) the quantity of C 0 2 evolved 
by a unit weight of growth was considerably less than in those which 
remained alkaline. 
It is evident that there are a number of factors which might have 
some influence on the evolution of C0 2 in experiments with a number of 
fungi. It is not possible to find an environment which would be the 
optimum for all of them. If one considers the concentration of the solu¬ 
tion alone with respect to the source of carbon, which Kunstmann 
showed to influence respiration, it is clear that a concentration which 
might be considered optimum for one organism might not necessarily 
be so for another. In spite of the great ability of fungi to adapt them¬ 
selves to solutions of high osmotic concentration, it is a well-known fact 
that some organisms can tolerate a more concentrated solution than 
others. The Penicillia, for example, grow in a sugar solution of high 
concentration. The writers found that Botrytis cinerea and Penicillium 
sp. grew equally well in a concentration of 38 per cent and 58 per cent, 
respectively. Bearing in mind the influence the concentration has on 
respiration one may readily conceive how the quantity of sugar present, 
which in these experiments was alike for all the organisms, might work 
to the advantage or disadvantage of the different fungi, at least so far as 
the amount of sugar required to produce 1 gm. of C0 2 is concerned. 
Other factors which conceivably might influence the results are (1) 
acidity of the solution, (2) spore sowing, (3) light, (4) temperature. As 
