214 BOTANICAL GAZETTE [MARCE 
here to be the optimal solution. The brook water solution was 
inserted here to add another solution to the number of those which 
allow so vigorous an ammonification owing to the low osmotic pres- 
sure. The artificial sea water, however, still remains far superior to . 
any other salt mixture thus far tried. 
SERIES VII 
In order to compare to the best advantage the various salt mixtures 
with the artificial sea water and distilled water solutions, it was 
decided to arrange in one series the best representatives of the single, 
binary, ternary, and quaternary salt solutions, along with the arti- 
ficial sea water and the distilled water peptone solutions. 
TABLE VII 
ALL QUANTITIES GIVEN REFER TO CUBIC CENTIMETERS OF 0.35 m™ SOLUTIONS 
PEPTONE CONTENT 0.91 PER CENT. 
Number Culture solution ppd a re pre 
t EABE pan NaN ee too NaCl 20.50 
- too NaCl 
nes eae 10 MgCl, 23.39 
too NaCl 
Gate 10 MgCl, } ° 25.88 
5 CaCl 
| 100 NaCl 
Beer ex va mot 28.42 
2 CaCl 
Poe eer Artificial sea water 31.41 
Oe Peptone in distilled water 42.51 
We see here to good advantage the beneficial effects of balancing 
solutions. Of the large variety of single salts and combinations of 
salts of various kinds, there was none that could quite approach in 
efficiency the artificial sea water or the natural sea water of the same 
concentration, and we are obliged. to accept the fact that for bacteria 
(or at least for that group represented by B. subtilis) physiologically 
balanced solutions are necessary if optimal development of the 
bacteria is sought for. 
DISCUSSION OF RESULTS 
The number of combinations of salts that could be experimented 
with in a manner similar to that above given is of course unlimited, 
