CHAPTER XXVII 

 THE VALUE OF GREEN PLANTS TO MAN 



Problems : To find out how green plants are useful to man : 



(a) As food. 



(h) In supplying material for clothing. 



(c) In other ways. 



To find out how green plants are harmful to man. 



Suggested Laboratory Work 



If a commercial museum is available, a trip should be planned to supple- 

 ment the work in this chapter. The school collection may include most of 

 the examples mentioned, both of useful and of harmful plants. 



A study of weeds and poisonous plants should be taken up in actual labora- 

 tory work, either by collection and identification or by demonstration. 



Home Project. A weed survey of my home yard or my neighborhood. 



Green Plants have a " Dollar and Cents " Value. — To the girl 

 or the boy living in the city green plants seem to have little direct 

 value. Although we see vegetables for sale in stores and we know 

 that fruits have a money value, we are apt to forget that the wealth 

 of our nation depends upon crops more than it does on manufac- 

 tories and business houses. The economic or " dollars and cents " 

 value of plants is enormous ; and our lives depend on the food 

 which they supply. 



We have already seen some of the uses to mankind of the prod- 

 ucts of the forest ; let us now consider some other plant products. 



Leaves as Food. — Grazing animals feed almost entirely on 

 tender shoots or leaves, blades of grass, and other herbage. We 

 realize the economic value of grass when we remember that for a 

 period of ten recent years the average hay crop in this country was 

 worth well over $1,000,000,000 a year. And this does not count 

 the wild grasses used for fodder by countless grazing animals. 



Certain leaves and buds are used as food by man. Lettuce, 



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