60 FOOD OF THE VEGETATING PLANT. CHAP. I. 



have been abstracted by the leaves of the Cactus. 

 From which it also follows that the leaves of vege- 

 tating plants do actually inhale oxygene, at least in 

 course of the night. 



Similar experiments on vegetating plants gave 

 similar results, but the quantity of oxygene ab- 

 stracted was not always in the same proportion. In 

 the present case it was very considerable, amounting 

 to three-fourths of the volume of the leaves, while 

 in other cases it was often not more than one-half 

 of their volume. 



SUBSECTION III. 



Nitrogene. Though nitrogene gas constitutes 

 by far the greater part of the mass of atmospheric 

 air, it does not seem capable of affording nutriment 

 Notave- to plants; for as seeds will not germinate in it, 

 food, 6 so neither will plants vegetate. It was regarded, 

 however, as constituting a vegetable food by some 

 of the earlier pneumatic chemists, particularly by 

 Priestley, who found, as it seems, that some sprigs 

 of Mint on which he had made the experiment 

 vegetated better in phlogisticated air than in either 

 dephlogisticated or common air;* and hence he 

 inferred that phlogisticated air, the nitrogene of 

 modern chemists, serves as a vegetable food.-f- In 

 this opinion he was followed by Ingenhoutz,^ 



* Priestley on Air, vol. iv. p. 327. f Ibid. vol. v. p. 13. 

 I Exper. sur les Yeg. vol. ii. p. 146. 



6 



