Mben tbe "MooDs are %ctiUQxcer\ 69 



You suggest, as another use, the suppl}^ of food. Yes, 

 the grasses and many herbage plants are greedily 

 browsed by annuals ; we owe to them our supply of 

 beef, mutton, milk, butter, cheese, and other articles 

 of food. Lettuce, cabbage, cress, parsley, are fa- 

 miliar examples of leaves eaten by man, while 

 endive, chicory, thyme, sage, dandelion, mustard, 

 are more or less used upon the table. 



We have not yet reached the most important 

 functions of the leaf. To the plant itself the leaf 

 serves as a food purveyor, gathering perhaps the 

 larger portion of plant food from air and moisture 

 by absorption. The leaf is also the main breathing- 

 apparatus of the plant ; the leaf spreads out to air 

 and sunlight the food matter received by the entire 

 plant, and thus secures chemical changes in it similar 

 to assimilation and digestion. The leaf makes pos- 

 sible the circulation of the sap. Thus the leaf serves 

 the plant as throat, lungs, and stomach. What the 

 human being would be without such organs the 

 plant would be without the leaf, or some part modi- 

 fied, as in the cactus family, to serve the purposes 

 of the leaf. 



How does the leaf perform its duties to the plant? 

 The root absorbs water, holding in solution various 

 mineral substances ; this rises as sap through the 

 tubes of the stem to the leaves. There it is spread 



