54 



AERATION AND AIR-CONTENT. 



Barthelemy (1874 : 175) gave a summary of the analyses of in- 

 ternal air in connection with his own determinations (table 21). 



TABLE 21. 



Wille (1889) found the air of Fucus bladders in water to contain 

 35 to 37 per cent of oxygen, 20.7 to 20.8 per cent in those dried in 

 air 10 hours, and but 2.7 per cent in those lying in the dark for 12 

 hours. Carbon dioxid was completely absent in all cases. 



Devaux (1889 : 115), studying the gas-exchange of aquatic plants, 

 made the analyses of the gas in and about the plant and of the air 

 shown in table 22. 



TABLE 22. 



The author concluded that the air dissolved naturally in water 

 possesses essentially the same pressure as in the atmosphere. As 

 to the internal air of the plants, if the water is normally aerated, the 

 air of the air-passages or spaces is nearly pure. The air arrives at 

 each cell with nearly the same pressure as that which it possesses 

 in the surrounding water and in the air-passages. There is some air 

 simply dissolved in the substance of the cell itself, and this possesses 

 the same pressure as at the exterior. 



In measuring the oxygen-content of a tubercle (1890 : 257), 

 Devaux concluded that the oxygen never wholly disappears in the 



