1921] 
ARMSTRONG—SULPHUR NUTRITION IN THE FUNGI, THIOSULPHATE 241 
about Py 5.2. The chemicals used were Merck’s Blue Label 
Reagents in all cases except the mono- and dibasic potassium 
phosphates in the experiments of 1915-17. 'The monobasic 
potassium phosphate was used without recrystallization in the 
first experiments, but in the later experiments a salt recrystal- 
lized several times that gave the Sórensen coefficient of Pg 
4.529 for a 1/15 molecular solution was employed in all the culture 
solutions. 
The Jena flasks and the 120-cc. Non-Sol flasks of the later 
series of experiments were carefully cleaned in an acid dichromate 
solution and thoroughly rinsed in distilled and redistilled water. 
Inoculations were made by transferring spores from a potato 
agar slant to 10 cc. of sterile distilled water until a heavy spore 
suspension was obtained. In the first experiments .2 cc. of this 
suspension was added under sterile conditions to each flask, while 
in the later experiments, .5 ec. of the inoculum was use 
All controls were uninoculated, sterile solutions whisk were 
kept under the same conditions as the experimental flasks. The 
salt and carbohydrate components of each solution are given on 
the basis of a 50-ec. culture. In all cases sufficient water was 
added to make the volume 50 cc. The production of H,S was 
determined by suspending in the neck of each flask a strip of ` 
filter-paper which had been soaked in lead acetate. These strips 
were sterilized by soaking in a nearly saturated simmering lead 
acetate solution and then transferred to sterile dishes. 
The determination of sulphates in solution was made by adding 
BaCl, after the solution had been acidified with dilute HCl to 
prevent the precipitation of phosphates. 
The titrations of the thiosulphate in solution were made with 
N/10 or N/100 iodine. This standard titration method furnishes 
a definite quantitative method for the determination of the 
thiosulphate decomposed by each organism. The starch and 
iodine solutions were prepared and standardized according to 
directions given in the ‘Analytical Chemistry’ of Treadwell and 
Hall. Ten ce. of the solution from each culture, to which was 
added 1 cc. of starch paste, were used in the titrations. Dry 
weights were obtained by drying to a constant weight in an oven 
at 105° C. 
To follow the successive changes in hydrogen-ion concentration, 
