162 STRUCTURE OP VEGETABLES. 



though its leaves are very similar in shape, has 

 them standing upright. 



Leaves are made up of a number of very fine 

 nerves, as they are called, and small tubes or 

 vessels, and of a delicate thready net-work. This 

 structure is very prettily seen, by picking up in 

 autumn the leaf of a poplar. After this has lain 

 for a time, it loses the soft matter, and becomes a 

 sort of skeleton, made up of membrane like very 

 fine net. Leaves serve the same purpose in the 

 vegetable kingdom, that lungs and other con- 

 trivances for breathing do amongst animals. The 

 air, when confined over a plant, is found to undergo 

 certain changes, and if not renewed, the plant dies. 

 Thus, a free circulation of air is as needful to the 

 life and health of vegetables as of animals. 



Questions, 



Do vegetables live ? 



To what do they appear sensible ? 



What objects are included in the vegetable kingdom? 



What is the structure of vegetables ? 



Describe the parts of vegetables as they may be seen in a 

 branch of elder. 



Are leaves alike in size and shape ? 



Are more leaves than one contained on one leaf-stalk in 

 some plants ? 



Of what are leaves composed 1 



What purposes do leaves serve 1 



Is a free circulation of air essential to vegetable life ? 



