[Vor. 8 
246 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the composition given below with only the thiosulphate varied: 
KH;PO, M/60, 2.2 cc.; (NH,)2 HPO, M/6, 2.2 cc.; KNO, MA, 
4.7 cc.; NH,NO, M/1, 12 ec.; MgCl, M/60, 2.8 cc.; CaCO, M/ 
100, 0.5 cc.; FeCl, M/1000, 0.5 cc.; dextrose M/1, 6.9 cc. Of the 
M/1 Na,S,0,, 10.1 cc. are used in the 5 per cent solution, 20.2 cc. 
in the 10 per cent solution, and 26.8 cc. of a 3/M Na,S,0, in the 
40 per cent solution. In every case sufficient water is added to 
make the volume of each culture 50 cc. 
In the series of increasing thiosulphate concentrations made up 
as 5, 10, and 40 per cent solutions, the growth of Penicillium was 
successively greater, as was the production of sulphates and H,S, 
though sporulation was prevented in the solution of highest con- 
centration. In the nutrient solutions employed, the inhibition 
of growth for Botrytis in the presence of the thiosulphate occurs 
between .6 and 2 per cent, for Aspergillus between 10 and 40 per 
TABLE IV 
GROW'TH OF CERTAIN FUNGI ON MEDIA CONTAINING POTASSIUM THIOCYA- 
NATE AND MAGNESIUM SULPHATE. TIME INTERVAL OF CULTURES, 27 DAYS 
Experiment 8 Experiment 9 
.2 per cent KCNS KCNS replaced by MgSO, 
Fungus A. nig. | P. gl. | B. ein. | Check | A. nig | P. gl. | B. cin. Check 
No. cultures 6 5 5 5 5 4 
Dry wt. (gms.) | .3512 | .1602 | .4155 .9212 | .4234 | 1.0766 
Sporulation 1 0 0 
H:S 0 0 0 0 0 0 0 0 
cent, while Penicillium grows very well on the 40 per cent solu- 
tion. These statements refer to solutions in which the hydrogen- 
ion concentration was unknown. In the later experiments it 
will be shown that the toxic concentration of a salt in solution 
may depend to some extent on the hydrogen-ion concentration 
of the medium. 
The nutrient solution employed was NH,NO, M/1, 6.2 cc.; 
KH,PO, M/1, 2.5 cc.; FeCl, M/1000, 0.5 cc.; sucrose M/1, 7.3 
cc. in each solution, with the magnesium and sulphur supplied 
n experiment 8 as 1 cc. each of M/1 MgCl, and KCNS. In ex- 
