CLIMATE FOR MAIZE 



205 



277. •Influence of Climate Upon Habit of Growth. — There is 

 greater variation in the habit of growth of the maize plant than 

 in any other cereal. These variations within any one of the five 

 types of maize seem to be correlated with the climatic condi- 

 tions as indicated by the great variation in size and in the time 

 of maturity in northern as compared with southern latitudes. 



The growing season for maize varies in different sections of 

 the United States from ninety to 160 days and varieties exist 

 which are adapted to these different growing periods. In gen- 

 eral it may be said that as we go north or south of a given lati- 

 tude a variety becomes one day later or earlier for each ten miles 

 of travel, the altitude remaining the same. That is to say, a 

 variety which ripens two weeks before a killing frost in a given 

 locality would only barely ripen if taken 140 miles farther north, 

 the altitude remaining the same. Care should be taken, there- 

 fore, in selecting new varieties, to get them from the same latitude. 

 If obtained from much farther north they may ripen too early 

 and consequently be too small. If obtained much farther south, 

 they may not ripen. 



Size and period of growth are also influenced by moisture. 

 Under conditions of favorable ^vater supply, the plant continues 

 to grow, while a deficiency will reduce growth and hasten ripening. 



278. Influence of Climate Upon Varieties. — Whether the environ- 

 ment was a cause of variation or whether selection, it is probable 



