290 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
tion contained 2.5 mg. zinc per cubic centimeter (i. e., 11.0 mg. 
ZnSO,7.H2O per c.c.). 
The flasks, each containing 50 c.c. of nutrient solution measured 
in a 50 c.c. graduate, were sterilized at 1414 lbs. for 20 minutes. 
Inoculations were from stock bread-cultures grown at room 
temperature (18-25? C.). Enough spores were added with a 
platinum loop to make a visible and apparently almost continuous 
layer on the solution surface. The A. niger culture used in these 
experiments was obtained originally from the “ International- 
stelle für Pilz-Kulturen, Amsterdam." Immediately after inocu- 
lation the flasks were placed in a dark cupboard at room tempera- 
ture (18-23? C.), or in the thermostat at 30-21 ° C. 
When harvested, the membrane, together with the op 
was thrown on a washed and weighed filter, washed with distilled 
water and dried ағ 103-105? С. for four days. 
The yields while given to the third place are probably reliable 
to two places only. 
2. THE EFFECT OF ADDING ZINC TO THE CULTURE MEDIUM 
Pfeffer solution: water redistilled through glass; “Crystal 
Domino” sucrose; NH4NO; (Merck); KH;PO, (Baker); MgSO..- 
НО (Merck). Room temperature (18-222 C.). Period of 
growth ten days. 
Kavalier Bohemian | Pyrex 
No zinc | то mg. Zn/L | No zinc | то mg. Zn/L 
| | Pe ee | 
0.317 grams | 0.888 grams 0.387 grams 0.864 grams 
33 d 0005“ 6.138. -“ о Е 
634r с^ 0.886 (5306 > 0:898 с. 
0.302 “ 0.880 0.286 “ 6.868. ^ 
0.314 0.924 : 0.325 o.903 “ 
одат“: | Боз ©“ | 0.326 “ 6.874... “ 
Here we see that in the Kavalier and Pyrex flasks the addition 
of zinc to the nutrient solution results in an increased dry weight, 
the increase being almost three-fold. 
3. THE INFLUENCE OF A ZINC GLASS (JENA) ON THE YIELD 
Pfeffer solution: water redistilled through glass; ‘Crystal 
Domino” sucrose; NH4,NO; (Merck); KH;PO, (Baker); MgSO..- 
“ 
