THE SEED 73 



This supposition brings us to the consideration of the 

 second of the three conditions of germination, denned 

 a little while ago, namely, the importance of air. Air, 

 as we know, consists of oxygen and nitrogen. Experi- 

 ments point to the fact that seeds require oxygen. A 

 seed buried deeply in the soil, or remaining under water 

 which is never changed, does not germinate ; but it 

 likewise does not germinate, or if already begun, the 

 process stops short, if the seed be surrounded with air 

 deprived of oxygen. It needs oxygen, undoubtedly. 

 Wherein, however, does the function of the oxygen 

 consist ? 



It is easy to prove that oxygen is absorbed by the 

 seed. Now oxygen maintains combustion ; in its 

 absence burning bodies become extinguished. There- 

 fore, if germinating seeds absorb oxygen and we leave 

 them for a certain length of time in a limited volume of 

 air, we shall deprive that air of oxygen and so rob it of 

 the property of maintaining combustion. Ten hours 

 ago we laid some germinating seeds at the bottom of 

 this wide-mouthed vessel, tightly closed with a glass 

 stopper. I open it now and introduce into it a burning 

 taper ; it is at once extinguished. Evidently the air in 

 this vessel does not contain oxygen any longer. The 

 oxygen has been absorbed by the seeds. 



Having observed before how close is the parallel between 

 the nutrition of seeds and animals, we may legitimately 

 raise the question whether also seeds do not use oxygen 

 for the same purpose as animals ? May they not use 

 it for respiration ? Respiration, as we all know, is in 

 its essence combustion. We inhale oxygen ; it is 

 carried by the blood all through the body, and oxidises 

 or burns up part of its carbon and hydrogen, giving 

 them off in carbonic acid and water. We can see this 

 in the following simple experiment, which proves that 

 the gases we inhale and exhale are different in kind, 

 and that the gas exhaled contains carbonic acid. The 



