402 BOTANICAL GAZETTE [ DECEMBER 
through the plant, and is harmless for any reasonable duration 
of experiment. It has, however, one theoretical disadvantage 
which has hitherto been overlooked, namely that, like any other 
crystalline salt, it dissociates in solution, and to an increasing 
extent with progressive dilution. Any given solution is then a 
little more than half as strong osmotically as one with twice the 
weight of dissolved saltpeter..* This objection might be over- 
come by making solutions according to the osmotic instead of 
per cent. strength, but since this source of error is less than that 
arising from the inaccuracy of the tests and the individual vari- 
ations of the plants and the cells, and the correction at best 
would only be relative, it seemed best to conform to the estab- 
lished method. Inthe reports of the experiments the expres- 
sion “turgor = 2.5 per cent.’ means that 2.5 per cent. KNO, 
is just sufficient to begin plasmolysis. 
THE EXPERIMENTS. 
Phaseolus multiflorus. Two series of cultures were carried 
through. The complete or standard ‘‘normal”’ solution was 
made by mixing, and diluting to one-twentieth, equal parts of 
the following solutions, prepared according to de Vries’ isotonic 
coefficients : 2 
Ca (NO;)2 9.876 % isotonic to 0.8 2q. KNO; 
KNO, 2.525 % or 0.25 #q. 
NaCl 1.462 % isotonic to 0.25 eq. KNO; 
K,HPO, 2.597 & Sp x 0.25 2q. KNO; 
MgSO, 4-464 % Ps ce 0.25 2q. KNO; 
A. Put in cultures November 23. Radicles 3-5 long. 
1. In normal solution. 
Nov. 23 Jan. 5 Feb. 13 
Stem a fics i Sa 50™ ae | 
: 2.5% 2.5-3% 25-35 
Rect jing 1o™ pk sone — 
. 2-2.5 % 2% 2% 
ee er sees oer =? per cent. 
solution. Kohlrausch, Wied. Ann. 26 2195. 
