BRIEFER ARTICLES 
A TROPISM CHAMBER 
(WITH THREE FIGURES) 
A few years ago the writer planned some classroom experiments to 
illustrate the geotropism of roots. 
Fic: 2 
The students wasted much time and 
many seedlings because of 
the wilting of the roots while 
they were transferring them 
to the observation chambers 
and fastening them to their 
supports. To overcome this 
difficulty some special tro- 
pism chambers were designed. 
These have given excellent 
satisfaction, and have proved 
to be so well adapted to the 
study of tropic responses 
that their use has suggested 
experiments, which would 
have been impracticable 
without this apparatus. 
The first makeshift con- 
trivance consisted simply of 
a Petri dish, 4-5 inches in 
diameter, with a small piece 
bottom, near one side. The 
dish was partly lined with 
wet filter paper. The seed- 
ling was pinned to the cork 
and the dish set on edge on 
top of an ordinary tumbler. The curvature of the top of the tumbler 
made a convenient support for the cover of the Petri dish. The Petri 
Botanical Gazette, vol. 60] 
[320 
