1924) 
WOLPERT—FUNGI AND H-ION CONCENTRATION OF MEDIA 45 
Good growth resulted when 0.25 per cent of sulphuric acid was 
added to this solution. When the same medium was made alka- 
line with sodium carbonate, no growth was obtained. 
The acidity of the medium has been shown by Falck (712) 
to be a conditioning factor for spore germination and for mycelial 
growth of species of Merulius. Furthermore, he has observed 
that growth and development of Merulius is more rapid upon 
wood previously infected by Coniophora cerebella than upon sound 
wood. Since mycelial growth of Coniophora cerebella makes the 
substratum decidedly acid, it is assumed that species of Merulius 
are partial to acid media. 
Wehmer (714) indicated that Merulius lacrymans increased 
the active acidity of the medium upon which it grew. Опе 
gm. of sound pine wood pulverized and boiled in 30 се. of water 
and titrated against 0,1 N NaOH! required 0.9-1.2 cc. to neutral- 
ize the solution. Decayed wood similarly treated required 4.9- 
8.0 се. for neutralization. 
Lenzites sepiaria, Fomes pinicola, Polystictus versicolor, and 
Polyporus lucidus, according to Zeller (716), did not grow upon 
slightly alkaline Thaxter’s glucose-potato-hard agar, while a 
readjustment to slight acidity resulted in good growth. This 
indicates for all of these species a marked intolerance to alkaline 
media. 
The hydrogen-ion concentration necessary to inhibit the 
growth of Lenzites sepiaria, Fomes roseus, Coniophora cerebella, 
and Merulius lacrymans upon synthetic and malt extract media 
was determined by Meacham ('18). While the 4 species show 
considerable fluctuation, they respond in much the same way to 
active acidity, showing maximum growth at approximately Ри 
3.0. A composite curve indicates good growth with increasing 
acidity until Рн 3.0-2.6 is reached. There is a distinct critical 
zone between Px 2.6 and 1.9 where growth decreases rapidly, 
followed by total inhibition at Ри 1.7. In general, these figures 
indicate a marked tolerance to high acidity. 
Schmitz (719) studied the hydrogen-ion concentration con- 
ducive to optimum growth for Fomes pinicola, Lenzites semara, 
It is assumed that this solution was NaOH, since Wehmer indieated it asa 1/10 
N. N. solution. 
