1921] 
ARMSTRONG—SULPHUR NUTRITION IN THE FUNGI, THIOSULPHATE 253 
The composition of the medium was as follows: NH,NO, M/1, 
6.2 cc.; KH,PO, M/1, 2.5 ec.; MgCl, M/1, 1.0 ec.; Na,S,0, M/1, 
1.2 cc.; sucrose M/1, 7.3 cc.; FeCl, M/1000, .5 cc.; water plus 
acid or alkali sufficient to make 50 ce. 
The addition of NaOH caused some precipitation in the me- 
dium but this was disregarded. 
Experiment 16.—-In following the successive changes in the 
cultures, quantitative determinations were made of growth, 
changes in Py, and the thiosulphate content of the solution, 
qualitative tests for H,S and sulphates, and observations on the 
sporulation of the cultures. The relations between growth, 
hydrogen ion, and the consumption of thiosulphate are more 
clearly shown in figs. 1, 2, and 3. Both Aspergillus and Botrytis 
show a rather meagre growth on this acid solution, while Peni- 
cilium grows very well, surpassing this growth in only one other 
solution, that of Pa 4.5. A series at Py 3.0 was inoculated but 
no growth was obtained with any of the organisms. 
If any direct relation exists between the decomposition of 
thiosulphate and the resulting growth, the ratio of thiosulphate 
to growth would be a constant and would appear as a straight 
line when plotted on coórdinate paper. If the possibilities of ex- 
perimental error are considered, there appears to be such a 
straight-line relationship in 8 of the 12 cases determined and 
represented in figs. 4, 5, and 6. Penicillium seems to exhibit the 
direct relationship between the decomposition of thiosulphate 
and growth in the series of cultures at initial Py 4.2, while 
Aspergillus and Botrytis exhibit the most extreme variations. 
The hydrogen-ion concentration of the solution does not appear 
to be the factor involved in these variations, as the hydrogen-ion 
concentration produced by Botrytis was lowest during most of the 
experiment and yet this fungus was the most inefficient user or 
decomposer of thiosulphate when dry weight is considered as a 
criterion of efficiency. In some of the other series of experiments 
it may be seen that a similar low production of acidity may not 
similarly affect the ratio curve. A point of interest is the de- 
cided reversion of the reaction in the solution supporting the 
growth of Penicillium. This decided reversion of the reaction 
occurred between the tenth and thirteenth days at the period 
when the mycelium suddenly produced a large number of spores. 
