148 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
The methods used by Shive (6) in his studies on the physiological balance 
of nutrient solutions for higher plants were used as a basis for this work. 
A number of radical modifications in these methods, however, were necessary 
on account of the physiological differences between the green plants and 
fungi. The most essential modification was in the composition of the nu- 
trient solution itself. In Shive's solution three mineral salts and a trace of 
iron constitute the nutrient material, and for green plants these salts contain 
all the necessary elements for growth. For fungi, however, a source of energy 
must be supplied in addition to the mineral salts, and in this work it was 
supplied in the form of cane sugar. A second necessary modification was 
in the treatment of the solution. In water-culture work with higher plants 
it is neither essential nor practicable always to use sterile solutions. With 
the fungi, on the other hand, it is essential that the medium be sterilized 
thoroughly before inoculating with the desired organism. The sterilization 
process as used for these experiments, however, probably caused very little 
alteration of the medium and may be overlooked as a factor influencing 
the medium itself. 
This work was outlined primarily to see whether the methods which 
Shive and others have used with such marked success in nutrition studies 
with green plants, would prove equally useful for similar studies with fungi. 
This work was carried out under the direction of Dr. J. W. Shive in the 
Laboratory of Plant Physiology at the New Jersey Agricultural Experiment 
Station. 
Experimental Methods 
The experiments herein discussed consist of two groups of cultures. 
Group I, comprising series i,2,and 3, contains Ca(N03)2 as the source of 
nitrogen and will be referred to as the Ca(N03)2 group. Group 2, comprising 
series 4 and 5, contains NaNOs as the source of nitrogen and will be desig- 
nated the NaNOa group. 
Aspergillus niger was grown in 250 cc. Jena glass Erlenmeyer flasks on 
50 cc. of a liquid medium containing three nutrient salts, cane sugar, and a 
trace of iron. Each culture throughout five series contained the same 
amount of iron and sugar, the iron being present in amounts equivalent 
to o.oi gram of ferrous sulphate per liter, and the sugar in amounts equiva- 
lent to 38.97 grams per liter of nutrient solution. 
In series i, the nutrient salts, KH2PO4, Ca(N03)2, and MgS04, are 
present in quantities sufficient to give a total calculated osmotic concentra- 
tion value of 0.5 atmospheres. The series consists of 36 cultures, each dif- 
fering from all the other cultures of the series in the proportions of the 
three nutrient salts. The 36 cultures represent all the possible proportions 
or combinations obtainable by varying the partial concentration of each 
of the salts by increments of one tenth of the total concentration. A full 
account of this method of studying the effects of salt proportions is given 
by Shive (6) and need not be further discussed here. 
