[Vor. 11 
44 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
tion? What are the changes in the hydrogen-ion concentration 
of the substratum caused by mycelial growth? The present 
paper attempts to answer these questions as completely as the 
available time would allow. 
HISTORICAL REVIEW 
Tubeuf (08) found that NaH.PO, in solution supported 
mycelial growth of Merulius lacrymans, while Na,HPO, and 
Na,PO, did not. Similar results were obtained with the acid 
and alkaline phosphate salts of potassium and ammonium. 
As the monobasic salts are acid and the dibasic and tribasic salts 
are alkaline, it is concluded that growth is inhibited in alkaline 
solutions but not in acid solutions. 
Rumbold (’08) was the first to determine the inability of the 
Agaricales as a group to grow upon alkaline media. The acidity 
of separate portions of 5.0 per cent gelatine and 0.5 per cent 
malt extract solution was so adjusted that solution 1 reacted 
red to litmus paper; solution 2, red-violet; solution 3, violet; 
solution 4, blue-violet; and solution 5, blue. Fifteen species of 
Agaricales including Schizophyllum commune, Lenzites sepiaria, | 
Pholiota adiposa, and Armillaria mellea grew extensively іп solu- | 
tions 1 and 2, somewhat less in solution 3, still less in solution 4, 
and not at all in solution 5. Solutions 1, 2, and 3 were considered 
by her to be acid; solution 4, neutral or very slightly alkaline; 
and solution 5, distinctly alkaline. It is known that litmus gives 
а positive red color in solutions which have an active acidity of 
Рн 5.0 or greater, a red-violet color when the Рн is approximately 
6.0, and a violet color close to Pa 7.0. А blue color is obtained in 
all solutions with an active alkalinity of Рн 8.0 or greater. From | 
this it is concluded that, while the organisms used by Miss | 
Rumbold did grow to some extent in a neutral or slightly alkaline 
solution the amount of growth was less than that obtained in | | 
solutions with initial acidities of approximately Рн 5.0 and 6.0. | 
Furthermore, growth was entirely inhibited in solutions which | 
were as alkaline as Рн 8.0. 2 
These same fungi grew rapidly in an acid medium consisting _ 
of: 100 cc. Knop’s solution, 3 gms. agar, and 5 gms. grape sugar. | 
! The recent and prevalent names have been used for all fungi under discussion. 3 | 
