116 TILLERS OF THE GROUND CHAP. 



1. Those cultivated for their seeds. 



2. Those cultivated for their roots or under- 

 ground stems ; and 



3. Those cultivated for their fruits. 



There are, of course, also plants like cabbages 

 and lettuces which are cultivated for their leaves ; 

 plants like cloves which are cultivated for their 

 flower buds ; those like cinnamon cultivated for 

 their bark ; those like sugar-cane cultivated for 

 their sap ; and so on. " Speaking generally, how- 

 ever, it is the seeds, the underground parts, and 

 the fruits which are important to man for food. 



Of these by far the most important are the 

 seeds, and this for several reasons. In the first 

 place, seeds contain, bulk for bulk, less water and 

 more food material than other parts of plants. 

 Another reason, which must have weighed much 

 with primitive man when he began to cultivate the 

 ground, is that the plants which produce the greatest 

 bulk of seeds are annuals, that is, they grow faster 

 than other plants, so that the cultivator does not 

 have to wait so long for his crop as if he were 

 growing fruit trees, for instance. 



But before saying more about the different kinds 

 of cultivated plants, we must say a few words about 

 food, so that there shall be no confusion in our 

 minds. In order that we may keep in health we 

 must have three different things in our food. The 



