PLANT PHYSIOLOGY 148 
be placed in the dark, or the flask covered with dark 
paper. 
117. Experiment 21.—Line a beaker with blotting- 
paper, damp it, and fill it with germinating seeds, 
packed round the bulb of a thermometer. Place beaker 
under a bell-jar, the thermometer passing through its 
cork. Put small dish of caustic potash in bell-jar to 
absorb any carbon-dioxide given off by seeds. Fix up 
another similar apparatus, using seeds killed by boiling. 
After a few hours compare the two thermometers. Rise 
in temperature of living seeds is due to respiration. 
118. Experiment 22.—Fill a test-tube with mercury, 
and invert it in a dish of mercury. Then slip two 
or three germinating mealie seeds under the test-tube. 
They will at once rise to the top, being lighter than 
mercury. Ina few hours the mercury will have sunk 
two or three inches in the tube, showing that some gas 
has been given out by the seeds. With a bent pipette 
force a little lime-water up to the top of the test-tube. 
Tt at once turns milky, showing that the gas given out 
by the seeds was carbon di-oxide. This experiment 
illustrates the phenomenon of intra-molecular respira- 
tion; the seeds were able to exhale carbon di-oxide 
without having any free oxygen; they must have ob- 
tained their oxygen from the decomposition of complex 
substances in the seeds themselves. 
119. Parasites.—Though the majority of green plants 
obtain their food from the carbon di-oxide of the air, 
and from salts in solution in the soil, there are a few 
exceptions. 
Parasites are plants which obtain their food from other 
