[Vor. 8 
272 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
production to the known faetors. For example, Aspergillus has 
produced H,S from every solution containing thiosulphate 
except the one with initial Py 4.5, lowest Py 1.7, where all the 
Ory wt. - 
cg $ : 
100 Roa 2 
PA ie 
80 f 3 
gær] ÉS 
60 F> EN 4 
> 
o 
^n / 
Lb 
0 4 8 12 16 20 
Days 
Fig. 17. Penicillium cyclopium on solution of initial Pa 4.1 con- 
taining magnesium sulphate. 
thiosulphate was decomposed and sulphates were clearly appar- 
ent. Penicillium has behaved similarly except on the solution 
with the initial P, 7.1, lowest Py 4.4, where the growth was 
good, yet with little of the thiosulphate decomposed. The initial 
acidity alone might be conceived as the limiting factor, for the 
