2 CLASSIFICATION, ORIGIN AND DISTRIBUTION 



and some 60 more, over ^,000 years ago. He classifies the species as 

 follows : 



Old World New World 



Cultivated for underground? parts 26 6 



Cultivated for stems and leaves 57 8 



Cultivated for the flowers or their 



envelopes 4 



Cultivated for their fruits 53 24 



Cultivated for their seeds 58 8 



Cryptogam cultivated for whole plant. . 1 



198 47 



New species are constantly being added to the list of useful 

 plants. Of most species, cultivated extensively, a great many vari- 

 eties have been developed. For example, with cultivated wheat 

 there are more than one thousand known varieties, and of maize or 

 Indian corn, at least five or six hundred varieties.. 



Classification by Use. Crops are very commonly classified 

 according to use, as follows : 



(1) Cereal or grain crops, as corn, wheat, oats, barley, or rice. 



(2) Legumes for seed, as beans, lentils, and peas. 



(3) Forage crops, as all grasses cut for hay, legumes cut for 

 forage, sorghum and corn fodder. 



(4) Eoots, as beets, turnips, and carrots. 



(5) Fiber crops, as cotton, flax, and hemp. 



(6) Tubers, as potatoes. 



(7) Sugar plants, as sugar beets and sugar cane. 



(8) Stimulants, as tobacco, tea, and coffee. 



Other crops not commonly classed as field crops would be the 

 fruits, vegetable crops, and timber crops. 



Important Botanical Groups. The most important botanical 

 group is the grass family (Graminece) to which all cereals except 

 buckwheat belong, and at present perhaps three-fourths of the forage 

 crops harvested are made up of grasses. The two families next in 

 rank are the legumes (Leguminosce) , so called because the seeds in 

 most cases are borne in a pod or "legume," and the nightshade 

 family (Solanacece) , to which belong the potato and tobacco. 



The Most Important Crops. The hay and forage crop is the 

 most valuable and extensive crop of the world, but is made up of a 

 great many kinds of plants. The world's most important plants are 



