THE SEED AND GERMINATION 45 
of a pickle bottle, place some bean seeds. Cork with a 
rubber cork or an ordinary cork well smeared with 
vaseline to keep out the air. When the seeds have been 
germinating for some days pour the gas from the 
bottle into a test-tube containing a little lime water, 
which, on being shaken becomes milky, indicating the 
presence of carbon dioxide. As we shall find later on, 
some of the carbon of the seed has been oxidised to 
supply the energy necessary for the development of the 
embryo. At this stage of the plant’s life, in the absence 
of chlorophyll, oxidation is the only available source 
of energy. 
Heat— Wherever oxidation takes place we may 
expect heat; but obviously the amount given off at one 
time by a single germinating seed would be too small 
sensibly to affect the thermometer. Fill two vessels 
holding at least a quart,-one with germinating peas, 
and the other with moist cotton wool. Cover each 
with a sheet of cardboard supplied with a hole through 
which a thermometer may pass. Extremely accurate 
instruments, in which the temperature readings exactly 
correspond, are needed for this purpose. Pass the 
thermometers through the openings, placing the bulb 
of one in the heart of the germinating seeds, the other 
in the cotton wool. Accurate observations, in which 
care is taken not to breathe on or touch the apparatus, 
will show that the mereury stands higher in the 
thermometer registering the temperature of the mass of 
germinating peas than in the other. The writer has 
never observed a difference of more than one degree. 
The vessels must not, of course, be placed in the 
sunlight. 
ESCAPING FROM THE COVER. 
All seeds do not escape from their covers in the 
same way. Practically all dicotyledons and some 
monoecotyledons back out of their covers, instead of 
