254 



PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



In figure 4 the combined eft'ect of rainfall and temperature 

 for the 10 days following the date of blossoming of corn at 

 Wauseon, Ohio, is indicated. This demonstrates that wet weather 

 at this time is nearly always favorable for a good yield of corn 

 and that dry weather is not necessarily unfavorable if it is ac- 

 companied by cool weather. But when warm weather accom- 

 panies the lack of rain the probability of a poor crop is close to 

 90%. 



Figure 4. Dot chart showing the combined effect of temperature 

 and rainfall during July upon the yield of potatoes in Ohio. 1860 to 

 1914. 



From the above it is shown that the critical period in the 

 growth of corn is for the ten days following blossoming. For 

 lo-day periods it is from August i to 10. and for calendar months 

 it for the month of July. If it were practicable to compute 

 the 60-year record of rainfall for the period from July 15 to 

 August 15 this would undoubtedly give the highest value of r in 



