CHAPTER XLI 

 SOME USEFUL PLANTS AND PLANT PRODUCTS 



490. Economic botany. The branch of the science which 

 treats of the uses of plants to man is called economic botany. 

 Since whole industries like agriculture, lumbering, paper making, 

 and a multitude of others are concerned with the utilization of 

 plants or parts of plants, the subject is a most extensive one and 

 can only be outlined in a general text-book of botany. 



A partial classification of useful plant products may be sug- 

 gested, dividing them into 



1. Food products for human use. 



2. Medicinal plants and plant products. 



3. Food products for domestic animals. 



4. Plants used as fertilizers. 



5. Plant products used in chemical and other manufactures, as tan- 

 ning, dyeing, etc. 



6. Plant fibers and related products. 



7. Timber. 



8. Fuel. 



9. Ornamental plants. 



In general only those members of the classes above given 

 which are of considerable importance in our own country will 

 be mentioned in this chapter. 



1. FOOD PEODUCTS FOE HUMAN USE 



491. The grains form the most important part of our vege- 

 table food ; they are the fruits of the cereals, or food-producing 

 grasses, and for this and other reasons the grasses, which in 

 all number about 3500 species, are more useful to man than 

 any other family of plants. The principal genera of cereals are 



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