Jan. 17, 1916 
Plenodomus fuscomaculans 
743 
containing magnesium sulphate in M/33 concentration. Conductivity 
water was used. Inoculation was made with a drop of spore suspension. 
After one month many (more than 50) pycnidia were found in the loose 
submerged mycelium. 
As a mineral base for nutrient solutions, monobasic potassium phos¬ 
phate and magnesium sulphate, along with other chemicals, were fre¬ 
quently employed. The net result of numerous cultures made in the 
attempt to find some hint of the value of this or that mineral was the 
conclusion that cultures with these two constituents alone, with a suitable 
nitrogen and carbon supply, gave as good results as more complex combi¬ 
nations. 
This solution of mineral salts contains the bulk of the elements generally 
considered essential for fungus growth. Carbon and nitrogen need to 
be added to secure the complete nutrient, but iron can be neglected, 
since it is such an unavoidable impurity in chemicals and is usually 
present as a constituent of the glassware. Beijerinck (Samkow, 1903) 
had used a similar solution as a culture medium for bacteria. 1 
Because of the extremely small amounts of minerals found necessary 
for growth and reproduction in this form, I modified the formula by 
cutting down the concentration of the various components. Since the 
solutions were to be used in comparative work, the chemicals were added 
on a molecular-weight basis. At the time of the first experimentation it 
was thought that the reaction should be approximately neutral, and 
accordingly molecularly equivalent weights of potassium acid phosphate 
and sodium carbonate were employed. Similarly, through dependence 
upon relations of other plants, it was thought that magnesium sulphate 
might be slightly toxic, and it was used at a lower concentration than 
either of the other two minerals. The solution thus devised for prelimi¬ 
nary experiments contained sodium carbonate and potassium acid 
phosphate as M/100 and magnesium sulphate as M/500. Subsequent 
experiment showed that the carbonate could well be omitted and the 
magnesium sulphate increased from fivefold to tenfold. 
The other combinations were used for comparison with this mineral 
base. The mineral constituents of Raulin solution and those of Dox 
solution were tried, and while either were suitable, neither had any 
advantage over this modified Beijerinck solution; on the contrary, they 
were much more complex and contained the mineral elements in excess 
of the needs of this fungus. 
Carbon supply. —The carbohydrates form the common source of 
carbon for fungi. Other classes of compounds, as pointed out by Nageli 
(1880) and Wehmer (1891), may be utilized. For this organism, as 
indicated in Table XXIII, other classes of compounds—but of alcoholic 
1 Samkow used the following base with a great variety of organic compounds: Potassium acid phos¬ 
phate, 2 gm.; sodium carbonate, 2.5 gm.; magnesium sulphate, 0.4 gm.; water, 1 liter. 
