194 VEGETABLE PHYSIOLOGY. [DEO. 



place under ground only, when the seed is almost 

 entirely deprived of light and air, which are, 

 you already know, essentially necessary to the 

 health of that portion of the plant which is 

 above ground. You will trace the seed from 

 the first period of its existence, in the bosom of 

 the flower, through its various stages, till it 

 becomes an individual, separate plant. 



After becoming acquainted with the natural 

 organs of plants, you will see how the sap, (ori- 

 ginally merely water, containing different crude 

 materials dissolved in it,) absorbed by the roots, 

 the extremities of which, for that purpose, 

 resemble little sponges, rises, every spring, 

 through the wood of the trees, and is conveyed 

 to the bud, which it developes, and to the 

 leaves, in which the evaporation of the useless 

 particles takes place, through pores furnished 

 lor that purpose. You will follow it in its 



