ATMOSPHERE. 



41 



al succeeding philosophers, that water, by virtue of the 

 vital energy of the plant, was sufficient to form all the 

 different substances contained in vegetables. 



But more recent experiments have proved that this 

 opinion is untenable, for it appears that in those cases 

 in which mere water supplies the wants of vegetation, 

 its invigorating effects are partially owing to the sub- 

 stances which it holds in solution. While we maintain, 

 therefore, that water is not the sole food of plants, and 

 is not convertible into the whole of the ingredients of 

 the vegetable substance, even with the aid of the vital 

 energy; we must at the same time admit that plants, 

 though vegetating merely in water, do yet augment the 

 quantity of their carbon. In this situation some plants 

 thrive, others are feeble, and languish for the want of 

 more solid nutriment ; and in all cases it is desirable 

 to know whether the vegetables we cultivate, grow 

 most luxuriantly in a moist or in a dry soil. The tex- 

 ture and form of their leaves and roots, and the pecul- 

 iar situation, in which, when unrestrained by culture, 

 they are found to delight, will furnish useful hints to 

 those who are pursuing this enquiry. 



2. ATMOSPHERE.— When it was found that wa- 

 ter is insufficient to constitute the sole food of pL.nts, 

 recourse was next had to the assistance of the atmos- 

 pheric air ; and it was believed that the vital energy of 

 the plant, is at least capable of furnishing all the differ- 

 ent ingredients of the vegetable substance, by means of 

 decomposing and combining in different ways, atmos- 

 pheric air and water. But as this extravagant conjec- 

 ture is founded on no proof, it is consequently of no 

 value. It must be confessed, however, that atmospher- 

 ic air is indispensably necessary to the health and vig- 

 or of the plant ; as may be seen by looking at the differ- 



