258 BOTANICAL GAZETTE [aPRi 
minimum, optimum, and maximum may be determined precisely, 
and all results tabulated and plotted in curves, an exercise of 
great pedagogic value to those beginning exact work in physi- 
ology. 
It may be thought that the thermometer, being further from 
the source of heat than the slide, may register a lower tempera- 
ture. This, however, is not appreciably so, as shown by one 
stage I had made with thermometer chambers both proximal 
Fic. 2.—A clinostat. 
and distal of the slide chamber: In this both thee 
registered practically alike unless the temperature peer 
raised with great rapidity, which is in any case not permis 
because of its abnormal effects upon the protoplasm. 
2. A clinostat. 4 illumi- 
It is most astonishing that so vastly important ‘a ttentio® 
nating a subject as irritability should receive S° little pe and 
as it does in our elementary courses. It is the — 
