300 The Botanical Gazette. [May, 
perature to the limit set by Darwin, no curvature of the ten- 
tacles was to be seen. The conduct toward temperature 
change varies, therefore, according to the nature of the sur- 
rounding medium, and causes aside from temperature are op- 
erative. He found, in fact, that distilled water at ordinary 
temperatures acted as a stimulus, and in a slight measure, the 
temperature elevation hastened and strengthened the reaction. 
From ecological considerations this conclusion is surprising. 
Distilled water prepared with the utmost care gave the same 
result, impurities being, therefore, in no way responsible. 
o test Darwin’s statement that leaves react more rapidly 
at higher temperatures, Correns used as irritants dilute solu- 
tions of sodium chloride (1:8400), sodium nitrate (1: 840) and 
acetic acid (1:333) at two temperatures, 18 to 21° C. and 48 
to 52 He found that the strength and speed of the re- 
action of Drosera leaves to chemical stimuli is increased by 
win. 
The author found that o. 1% calcium nitrate entirely oe 
vents any reaction; 0.02% still exerts a noticeable influenc*, 
0.01% is without apparent effect. 
Drosera leaves seem to react in an especially p 
manner to ammonium carbonate in dilute solution (0.05%), 
A comparison of effectiveness in their specific directions ’ 
calcium nitrate and of ammonium carbonate showed that 
five to ten parts of the former are necessary to phy siologica'y 
balance one part of the latter. : 
The growth habits of Drosera rotundifolia stand in 
with the above results since this plant with its comp 
the sphagna, are tound only in soils poor in lime. 
of Drosera watered with hard water quickly die.—R 
H. TRuE. 
ronounced 
accord 
anions; 
ultur 
ODNEY 
