75° 
Journal of Agricultural Research 
Vol. V, No. 16 
The experiment shows in a striking way how unlimited the possible 
combinations of nutrients may be. The marvelous thing is the absolute 
regularity of the product, regardless of this or that varied food supply. 
Growth that morphologically could not be distinguished arose from a 
protein or a mineral nitrate. Pycnidia were produced from these widely 
divergent compounds, with carbon compounds equally separated, and 
in' these were billions of spores which did not differ in a manner per¬ 
mitting measurement, each a potentiality which could repeat indefinitely 
under these conditions the same reaction. 
Prom this experiment we may pick a combination which is favorable 
for growth, but which also gives an abundance of pycnidia. For fur¬ 
ther experiments the combination of minerals with maltose and asparagin 
was chosen. The steps, more or less logical, which lead to the develop¬ 
ment of this synthetic culture solution may be reviewed. Experiment 
had shown that the essential mineral elements necessary for the growth 
and development of this fungus were contained in two mineral salts. Ex¬ 
periments in which these are added to various nutrient solutions give a 
hint as to the value and the concentration suitable. Eventually a com¬ 
pound was selected which gave the mineral salts which needed to be 
supplied and in addition had a chemical which could be used to make the 
reaction less acid, as desired. Previous work had shown that the 
organism could grow and produce pycnidia on extremely limited amounts 
of minerals, so the amounts taken were extremely small—far smaller 
than the ordinary formulas call for. In choosing the carbohydrate, 
wide choice was possible, since so many allowed good growth. Maltose 
was selected for use in the experiment just reported, because, next to 
xylose, it had given the best growth. The use of xylose was not advis¬ 
able because of its high cost, but care was taken to use maltose in small 
amount, so that the effect found in the experiment reported in Table XX 
would not be repeated. Accordingly, M/ioo concentration was pro¬ 
visionally chosen. The device for deciding upon the nitrogen source 
has been detailed in the preceding experiment. The low concentration 
of nitrogen was chosen to avoid such toxic conditions as were found in 
the pea broth. In passing, it may be said that an attempt was made to 
secure approximately the ratio of carbon to nitrogen that exists in the 
com broth, which had been found extremely favorable to the organism. 
Different concentrations of the separate constituents of this nutrient 
solution were further tested, with extremely interesting results. The 
device used was to vary the concentration of one constituent while 
holding the others constant. It was thought that in this way approxi¬ 
mately the optima for all the constituents could be found. 
The following experiment was performed with double-distilled water 
(slightly poorer than conductivity grade) and “non-sol” glass flasks. 
Dilutions were prepared as outlined in the table, and the culture media 
