2o6 THE CEREALS IN AMERICA 



that there is a relation between climate and existing varieties 

 of maize. The time that it has taken to fix these types is, how- 

 ever, a matter of much difference of opinion and about which 

 the evidence is obscure. The variations as to size and maturity 

 existed when this country was discovered. It is a common 

 observation that the varieties of a given region tend to assume 

 a common type. When dent varieties are introduced in a region 

 growing flint varieties, or the reverse, the introduced variety 

 tends to take on the characters of the other type. This has 

 been attributed to climatic influences, but may be explained 

 upon the grounds of crossing and unconscious selection. The 

 current cross would not, ordinarily, show in the seed, but would 

 show in the resulting crop. Varieties sufficiently distinct to 

 escape cross-pollination have been grown continuously without 

 modification.' 



The author had a standard variety of maize grown about 120 

 miles north of the Illinois Station for three years. The first 

 season it barely ripened in its new location. The ripest ears 

 were selected for seed, and in subsequent years it was believed 

 by the grower to have ripened earlier. After three years seed 

 was returned to the Illinois Station and on the fourth year 

 grown beside seed continuously grown at the station. When 

 thus grown side by side ' there was no difference in the time of 

 ripening. The evidence concerning the influence of climate 

 upon varieties is not as clear as might be desired, but it is 

 probable that much that has been ascribed to climate has been 

 due to selection. 



279. Influence of Climate Upon Composition. — Analyses so far 

 reported do not indicate any material difference in composition 

 in maize grown in different sections of the country covering a 

 wide variation in soil and climate. An average of thirty-five 

 northern and forty-nine southern grown samples of dent maize 

 has shown the following composition ; 



1 Cf. Bui. Torn Bot. Club Vol. XXI (1894), No. 12, p. 521. 



