(Vou. 11 
90 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
have much to do in determining whether the acidity will be in- 
creased or decreased as a result of mycelial growth. Except 
for Lenzites sepiaria and Polystictus versicolor, a substitution of 
peptone with its organic nitrogen for an inorganic nitrogen as 
well as а reduction in the amount of sugar tends to reduce the 
acid production by the fungi. Furthermore, while it is not always 
possible to predict the direction of the changes in acidity, it has 
been observed in these experiments that those solutions with 
a low initial acidity become more acid, and those with a high 
initial acidity become less acid. Temperature, on the other 
hand, may result in slight variations which are not possible 
to regulate or to express in any rule. The tendency of Pholiota 
adiposa to increase the active acidity of the peptone solutions at 
15° C. and 35° C. and to decrease it at 25° C. well illustrates 
this point. 
It is not possible to draw conclusions showing that those 
species tolerant to alkalinity produce a low final acidity or that 
those species tolerant to a more acid substratum produce a high 
final acidity. Pleurotus ostreatus does show an outstanding low 
final acidity in the peptone solution but not in the Richards’ 
solution, while Polyporus adustus and Schizophyllum commune 
do not have a final acidity different from that for the majority 
of the fungi intolerant to alkalinity. Lenzites sepiaria, previously 
shown to be the most active acid producer under all conditions 
in the 2 major solutions, shows no tendency to grow on a solution 
more acid than Pg 3.0. 
No one temperature ean be shown to be the optimum for 
all the fungi under all conditions. Тһе same temperature шау 
not be optimum for growth under different sets of conditions. 
This is well illustrated by Lenzites sepiaria, for in the peptone 
solution it is impossible to indicate any one temperature аз 
optimum for this fungus, while in the Richards’ solution it is 
evident that 35° C. is the best of the3. It is more probable that 
there are optimum ranges of temperature rather than optimum 
points, and that these ranges vary with the fungi under considera- — | 
tion. Furthermore, these zones may overlap one another and | 
шау be widened or narrowed, depending somewhat upon the 
environmental and physiological factors governing growth. The 
