30 BOTANICAL GAZETTE [JANUARY 
In comparison with this, a sect of the same concentrations of solution, 
in the same kind of bottle (500°°) but containing no sand, were set 
up. The plants were grown the same leagth of time, ia the same 
external conditions, and gave the following results: In 2/62500 and 
n/12500 good growth was obtained, but in all solutions of greater 
concentratioa plants all died. It is quite evident, therefore, that the 
quartz added reduced the toxic effect of 2/100, n/500, and n/2500 
to something less than 1/2500; perhaps, as is shown by the first 
series of solution cultures, to something less than n/1oooo. This 
conclusion is also drawn from the fact that roots, stems, and leaves 
were as vigorous in n/2500+quartz as were the plants in m/12500 
solution alone. 
After filtering away sand the solutions were again used in solution 
cultures in small black bottles (70°°) with the following results: 
| | 
| 5n n | n | n | n | 
dade | | be os —— 
| 100 | 100 500 2500 | 12500 62500 
easie aetan 
Average length of sprout, cm. . .| 0.0 La gas | 10.9 12.2 pe 11.3 
This shows that is it not necessarily the presence of the quartz af 
the time of growth which reduces the toxicity, but that quartz having 
stood in the solution has taken out some of the poison. Here, as 
in a previous experiment, the titration failed to yield quantitative 
results. The conclusion, however, is inevitable that quartz does 
remove considerable quantities of silver nitrate from solution, or at 
least renders it inert. 
ZINC SULFATE 
The series shown in figs. 18, 19 has the same arrangement and 
Fic. 18.—Zinc sulfate series in scil. Sept. 19-25. 1905. 
concentration of ZnSO, as that shown and explained in jigs. 15, 1 6 
for AgNO,. 
