PAET III. 



ON THE ORGANS OF NUTRITION IN PHANEROGAMOUS PLANTS. 



VEGETATION, in the more highly organized and complex 

 forms which it assumes in flowering plants, consists essentially 

 of a continuous axis or trunk, which developes in two opposite 

 directions, and is more or less ramified at its two extremities. 

 The superior or ascending portion of this vegetable axis is. 

 called the stem, the inferior or descending portion the root, 

 and the point of departure of either axis the collet or neck. 

 This neck is usually distinctly visible when the embryo plant 

 first rises from the ground ; after the cotyledons, or first pair 

 of young leaves, have developed, it disappears, and becomes a 

 merely imaginary line of separation between the base of the 

 stem and the root. 



These two extremities of the vegetable axis are beautifully 

 adapted to the earth and atmosphere, the two grand sources of 

 all vegetable nutrition. The aerial portion of the plant is 

 provided with leaves, by which food is taken in from the 

 atmosphere, and also with flowers, which are the organs of 

 reproduction ; the subterranean portion is furnished with a 

 quantity of fibres or smaller roots, which make their appearance 

 in proportion to the requirements of the plant and the barren 

 or fertile nature of the soil in which it grows. This vegetable 



