Experiments on Plants 795 



B. 8 gm., normal pressure, ordinary air, bell of 1840 cc. 



June 3. No germination. Air changed in B. and oxygen changed 

 in A. After this, the air in A contains 46.2% of oxygen, the pressure 

 is dropped to 3 atmospheres; the tension then is 138, that is, a little 

 less than 7 atmospheres. 



June 7. A. A very few radicles; the pressure has fallen fo 2 

 atmospheres; the air contains 2% of CO, and 41.2% of oxygen. 



B. The shoots are 3 to 5 cm. high and are very green. The air 

 contains 8% of CO, and 11.2% of oxygen. 



Assuming for A an average pressure of 2 V% atmospheres, we find 

 that in 4 days, the seeds in A have consumed, per 10 gm., 136 cc. of 

 oxygen, and those in B 225 cc. 



The seeds in A are sown on wet earth and develop. 



Table XVII summarizes the principal results of the experiments 

 above. They are arranged by the increasing order of oxygen ten- 

 sions expressed in atmospheres. 



The different methods used agree in showing that even a slight 

 increase in oxygen tension acts unfavorably on germination; be- 

 ginning with two atmospheres or 40% of oxygen, it is manifestly 

 delayed. 



At 5 atmospheres, which corresponds to pure oxygen, the delay 

 in germination is very great. 



Above 7 atmospheres, the seeds merely send out a few radicles, 

 no stalk appearing. 



Finally, at about 10 atmospheres, the barley seeds, when brought 

 back to normal pressure, are dead and do not germinate, whereas 

 cress seeds are resistant and sprout, although somewhat slowly 

 (Exp. CCCLXXX) . 



Now cress seeds have thin, dry cotyledons and contain no albu- 

 men. I wondered whether the death of the barley seeds did not 

 result from some chemical change in their considerable albumen 

 content. 



My experiments on fermentation, which will be reported in this 

 chapter, have convinced me of the truth of this hypothesis. Besides, 

 we see by Experiment CCCLXXI that fleshy seeds like those of the 

 castor bean and melon were much more affected by the pressure 

 than those of the marvel-of-Peru, which are more like cress seeds. 



In conclusion, I call attention to the fact that to obtain conclu- 

 sive results, the seeds must be wet. Otherwise, the oxygen, in 

 spite of the high tension, would not kill them. Example: 



Experiment CCCLXXXII. July 19. Dry wheat placed in a flask; 

 in another, wheat previously moistened, which however is not covered 

 with water, 



