SECT. III. EXTRACT. 65 



hirsutum, Lythrum Salicaria, and Polygonum 

 Per sic aria, vegetated indeed as in common air: 

 but at the end of six weeks of experiment, they 

 had neither decomposed the oxide constituting 

 their atmosphere, nor diminished its quantity.* It 

 cannot, therefore, be regarded as favourable ta ve- 

 getation. 



SECTION III. 



^ Vegetable Extract. 



WHEN it was found that atmospheric air and 

 water are not even conjointly capable of furnishing 

 the whole of the aliment necessary to the develope- 

 ment of the plant, it was then alleged that, with 

 the exception of water, all substances constituting 

 a vegetable food must at least be administered to 

 the plant in a gaseous state. But this also is a con- 

 jecture unsupported by proof; for even with re- 

 gard to such plants as grow upon the barren rock, 

 or in pure sand, it cannot be said that they receive 

 no nourishment whatever besides water, except in a 

 gaseous state. Many of the particles of decayed 

 animal and vegetable substances which float in the 

 atmosphere and attach themselves to the leaves, 

 must be supposed to enter the plant in solution 

 with the moisture which the leaves imbibe ; and 

 so also similar substances contained in the soil must 



* Sur la Veg. chap. vi. sect. iii. 

 VOL. II. F 





