INDIAN CORN. 157 



any of our farm crops. The differences in size be- 

 tween the corn of northern and southern latitudes has 

 already been mentioned. These differences existed 

 when the country was discovered, and we have no 

 evidence that varieties have been modified in modern 

 times by climate alone. 



Differences in the number of days required to ma- 

 ture a variety exist similar to the differences in size. 

 The smaller varieties require less and the larger more 

 time. The time may vary, at least, from 90 to 150 

 days in different parts of the country. 



In general it may be said that as we go north or 

 south of a given latitude, a variety becomes one day 

 later or earlier for each ten miles of travel. That is 

 to say, a variety which ripens two weeks before a kill- 

 ing frost in a given locality, would only barely ripen if 

 taken 140 miles farther north, the altitude remainino^ 

 the same. Care should be taken, therefore, in select- 

 ing 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 

 from much farther south they may not ripen. 



Professor Brewer shows that nearly nine-tenths of 

 the crop of 1879 was grown where the July temper- 

 ature is between 70 and 80 degrees Fahrenheit. 



Rain- fall affects the yield of com more directly than 

 does the temperature, while the temperature more 

 directly affects the matui'ity of the crop. The best 

 condition for the growth of corn is comparatively 

 heavy rains at considerable intervals, with clear 

 weather in the meantime. Twenty inches of rain-fall 

 are desirable during the five corn -growing months; 

 May, June, July, August and September. 



