252 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



Table 3. The Most Impotant Periods for Rainfall in the Develop- 

 ment OF the Corn Crop in Central Ohio. 1891 to 1910. 



Correlation 



Coefficient Probable 



Period. Most important. (r) it Error.. 



For 10 days. August 1 to 10 0.52 0.10 



For 20 days. July 21 to August 10 0.50 0.10 



For 30 days. July 11 to August 10 0.49 0.10 



For 40 days. July 11 to August 20 0.60 0.09 



For 50 days. July 1 to August 20 0.59 0.09 



In making the correlations from which table 3 was obtained, 

 the ten day periods were for each successive ten days, i. e,, 

 June I' to 10, June 11 to 20, etc. In making the 20-day corre- 

 lations the periods were' for each 20 days beginning June i, 

 June 10, June 21, etc. The longer periods overlapped as in the 

 20-day grouping. 



The correlation coefficient for the 10 days from August i 

 to August 10 was considerably higher than for any other 10 days 

 thus showing that this is the most important ten days in the 

 latitude of central Ohio, in the growth of the corn crop. In the 

 longer periods the value of r as indicated in table 3 was not 

 much greater than for one or more nearby groups. 



In order to ascertain what relation the above mentioned 

 periods bore to the growth period of corn, table 4 has been taken 

 from the Wauseon. Ohio, phenological data, referred to on 

 page 245. 



Table 4. Phenological Dates Relative to Corn Recorded at 

 Wauseon, Ohio. 1883 to 1912. 



Date corn was Average. Earliest. . Latest. 



Planted May 14... April 26... June 18. 



Above ground May 23... May 6 June 23. 



In blossom July 25 July 10 Aug. 6. 



Ripe Sept. 13... Aug. 30... Oct. 10. 



From these data and the meteorological observations taken 

 at Wauseon tables 5 and 6 have been prepared. The total effective 

 heat or "thermal constants" was determined by getting the sum 

 of the daily temperatures above 43 F. 



