CHAPTER XV 



WHY MAN CULTIVATES PLANTS 



Therk are about two hundred thousand known species 

 of plants in the world. When we compare this vast num- 

 ber with the few that man has chosen to cultivate, we are 

 led to ask : Why are these few useful to him, and what part 

 or parts of them are deemed so desirable that he is willing 

 to labor dihgently and patiently often for months or even 

 for years in order to secure them ? 



106. Classes of Plants according to the Parts for which 

 they are cultivated. — We may classify plants roughly 

 according to the portions from which the useful parts 

 come. Most of those that are cultivated by man may be 

 grouped under five heads as shown in the outUne below : 



I. Plants cultivated for their Grains which furnish Food 

 for Man and Domestic Animals. — These plants include : 



(1) Corn. 



(This crop will be studied in Chapter XVI.) 



(2) Wheat. 



(3) Oats. 



(4) Barley. 



(5) Rye. 



(6) Rice. 



(These crops will be studied in Chapter XVII.) 



//. Plants grown for Forage and Pasture for Domestic 

 Animals, the Useful Part coming from the Stems and 

 L 145 



