PLANT BREEDING 181 



3. The varieties distinguished by such characters as are 

 mentioned in the preceding paragraph often differ much in 

 their economic value, which depends on such qualities as pro- 

 ductiveness, resistance to drought, resistance to rust, and the 

 grade of flour which they produce. 



4. Varieties usually come true from the seed, so that, when 

 one has been chosen and isolated, it may be grown indefinitely 

 with little change. 



172. Variation in corn. Indian corn is preeminently an 

 American plant. At the time of the discovery of America, 



FIG. 156. A prize ear of Johnson County White corn 1 

 An admirable type of dent corn. Photograph by L. B. Clore 



and probably for a long period before that time, it was grown 

 by the Peruvians, by the Mexicans, and by many tribes of 

 Indians. It is supposed to have originated in South America 

 or Central America, near the west coast. Varieties of corn 

 differ greatly in size (from 1^ to 22 feet high) and in the 

 time required for maturing. Some corn in Paraguay is said 

 to ripen in one month, while Illinois field corn requires from 

 four to five months. 2 



1 This ear of corn was bid in by the grower (Mr. Clore) at an auction sale 

 of exhibits at the Chicago National Corn Exposition in October, 1907. The 

 price paid was $250. 



2 See Bulletin 57, Office of Experiment Stations, U.S. Dept. Agr., 1899. 



