4S OF CARBON. 



the plant possesses no organs for absorbing, 

 the carbonic acid from the atmosphere, the 

 substance of the seed itself, as before stated, 

 furnishes the necessary pabulum for the for- 

 mation of the root, which once formed imme- 

 diately performs the functions of the leaves as 

 well as root, by absorbing the carbonic acid 

 gas given off by the surrounding decaying 

 vegetable matter, as well as moisture, and the 

 other ingredients of the soil; and as the leaves 

 and other parts of the plant are developed, 

 nutrition is derived by the plant both from the 

 roots and the organs above the ground, and in 

 this stage it advances rapidly to maturity, but 

 when the plant is quite matured and the organs 

 by which it derives its supply of food from the 

 atmosphere are quite perfected, the carbonic 

 acid gas of the soil is no longer required. De- 

 ficiency of moisture does not now arrest the 

 progress of the plant, provided it is enabled to 

 derive from the atmosphere and dews suffi- 

 cient for the purposes of assimilation, and car- 

 bon during the heats of summer is derived ex- 

 clusively from the atmosphere. 



When the supply of food to a plant is greater 

 than it requires for the development of its or- 

 gans already existing, the superfluous nutri- 

 ment is not returned to the soil, but is em- 

 ployed by the plant in the formation of new 

 organs and in increased luxuriance. At the 

 side of a cell already formed, a new cell arises, 

 at the side of a branch and leaf a new branch 

 and leaf are developed, and these new forma- 

 tions owe their existence entirely to an excess 



