Note on a Method of demonstrating the Heat of 
Respiration. 
BY 
M. C. POTTER. 
With one Figure in the Text. 
T HE method of demonstrating the heat of respiration described In most 
text-books follows that devised by Sachs and, one is tempted to 
think, is frequently quoted without practical trial. In this method a number 
of germinating seeds are placed in a funnel supported in a beaker which 
contains an alkaline solution to absorb the C0 2 . The funnel and seeds are 
covered by a bell-jar to protect them from external variations of temperature, 
a tubule at the summit of the bell-jar serving for the introduction of a 
thermometer and for ventilation. A similar apparatus with a thermometer 
plunged in seeds which have been killed by boiling is used as a control. 
This contrivance is very inconvenient. A funnel sufficiently large for the 
purpose of the experiment necessitates a large bell-jar, and thus the apparatus 
becomes both expensive and cumbersome. For various reasons it cannot 
always be depended upon to give satisfactory results, and, as the heat of 
respiration is an important laboratory experiment, it may be of some interest 
to describe a simple apparatus which I devised and have used for many 
years with success. 
In every experiment certain precautions must be taken to guard against 
experimental error. In the directions usually given to demonstrate the rise 
of temperature consequent upon respiration, the calibration of the thermo- 
meters and the necessity for guarding against the variations of temperature 
of the surrounding air are generally noted. But no account is taken of any 
increase of temperature due to fermentation or putrefaction. This calls for 
special comment, and neglect of this factor may give rise to serious error. 
Thus when seeds merely killed by boiling are used as the control (as is 
commonly recommended) putrefaction generally takes place, and it is often 
found that the experiment apparently does not succeed as the control 
registers the higher temperature. 
[Annals of Botany, Vol. XXXI. Nos. CXXIII and CXXIV. July and October, 1917-] 
