THE SEED AND ITS GERMINATION. 9 



Remove the shells carefully from a considerable number of sunflower 

 seeds.i Try to germinate one lot of these in water which has been boiled, 

 to remove the air, and then cooled and poured into a bottle which it fills 

 up to the (tightly fitting) rubber stopper. In this bottle then there will be 

 only seeds and water, no air-space. Try to germinate another lot of 

 seeds in a bottle half filled with ordinary water. 



13. GerTnination involves Chemical Changes. — If a fjh.er- 

 mometer is inserted into a jar of sprouting seeds, for instance 

 peas, in a room at the ordinary temperature, the peas will be 

 found to be warmer than the surrounding air. This rise of 

 temperature is at least partly due to the absorption from the 

 air of that substance in it which supports the life of animals 

 ■ and maintains the burning of fires, namely oxygen. 



The union of oxygen with substances with which it can 

 combine, that is with those which will burn, is called oxi- 

 dation. This kind of chemical change is universal in plants 

 and animals while they are in an active condition, and the 

 energy which they manifest in their growth and movements 

 is as directly the result of the oxidation going on inside them 

 as the energy of a steam-engine is the result of the burning 

 of coal or other fuel under its boiler. In the sprouting seed 

 much of the energy produced by the action of oxygen upon 

 oxidizable portions of its contents is expended in producing 

 growth, but some of this energy is wasted by being trans- 

 formed into heat which escapes into the surrounding Soil. 

 It is this escaping heat which is detected by a thermometer 

 thrust into a quantity of germinating seeds. 



13. Experiment 5.* Effect of Germinating Seeds upon the Sur- 

 rounding Air. — When Exp. 4 has been finished, insert into the air above 

 the peas in the second bottle a lighted pine splinter, and note the effect 

 upon its flame. 



Besides the proofs of chemical changes in germinating 

 seeds just described, there are other kinds of evidence to the 

 same effect. 



1 These are really fruits, but the distinction is not an important one at this point. 



