436 
Potter. — Note on a Method of 
For the success of this particular experiment under any method, the 
following conditions must be satisfied : 
(a) a sufficiently large number of seeds so that the heat produced may 
not be dissipated ; 
(b) a supply of oxygen ; 
(i c ) a means of escape for the C 0 2 ; 
(d) screening from the changes in temperature of the surrounding 
air ; 
(e) efficient control ; 
(f) the prevention of putrefaction. 
The form of apparatus which I have found convenient consists of flasks 
of about 500 c.c. capacity with a short ventilation tube fused at the base for 
the escape of the C 0 2 , these being enclosed in a box and packed with cotton- 
wool (in annexed figure, A). By this means the first four conditions 
enumerated can be satisfied. 
I invariably employ three of these flasks. The first (I) contains living 
seeds thoroughly soaked before introduction into the flask. The second (II) 
contains seeds soaked and then boiled to 
destroy their power of germination. The 
third (III) contains seeds soaked and boiled 
in a solution of 0*5 per cent, mercuric chloride, 
with the object of killing the seeds and at the 
same time effectually sterilizing them. 
To soak the seeds before introduction 
into the flasks is a necessary precaution, 
especially if peas are used, otherwise they 
would swell and break the flasks. The usual procedure is to soak the 
seeds for II and III and then effect the necessary boiling, and while these 
are cooling to soak the seeds for I. In this manner it is possible for the 
experiment to commence with the three flasks at the same initial tempera- 
ture. Since the germinating seeds in I are damp, it is necessary that the 
control seeds should be damp also, in order to minimize any error due to 
the loss of heat from evaporation. 
The three flasks thus prepared are placed in a box and packed round 
with felt or cotton-wool. It may be safely assumed that any variation of 
temperature due to evaporation or to changes of room temperature will be 
common to the three flasks. 
Flask III is the control. In an ordinary room or laboratory its tem- 
perature will fluctuate, but does not rise above that of the room, and any rise 
above this room temperature in the other flasks will be due to respiration in 
I or putrefaction in II. 
Flask I gradually rises in temperature as the activity of respiration 
proceeds, and in the course of about forty-eight hours (if peas are employed) 
