MICHIGAN AC .\I)K.M> Ol" SCI IINCK. 169 



Fortunately the last few years liave seen an awakening along this line 

 of investigation, under the leadership of such men as Prof. J. Warren 

 Smitli, formerly in charge of the Weather Bureau Office, Columbus, Ohio, 

 and now at the head of the newly established division of "Agricultural 

 Meteorology" at the Central Office of the Weather Bureau at Washing- 

 ton. The establishment of this new division which concerns itself largely 

 with weather and resulting crop conditions, is in itself significant of the 

 fact that the importance of the relationship is being recognized. Prof. 

 Smith- has worked out some very practical and interesting relations be- 

 tween weather conditions and crop production, especially in regard to 

 rainfall and corn and potato yields. 



Prof. Cleveland Abbe'' in his "First Report on the Relations Between 

 Climates and Crops," compiled a complete survey of all investigations 

 which had been undertaken up to 1891, along this line, and I must simply 

 refer to that work for a history of the researches which had been made 

 up to that time, in regard to the matter of temperature and plant growth. 

 Suffice it to say that the method used more than any other was one called 

 the summation process. This consisted simply in adding together the 

 daily readings, usually the mean temperature of the day, from the time 

 of planting, for instance, until harvest, thereby establishing what has 

 been called a "thermal constant." It was reasoned that this sum of tem- 

 perature should be the same year after year, as it represented tlie 

 amount of heat required by the plant. But it was found not to be a 

 "constant" at all, varying considerably from year to year. The first 

 modification of this process was the introduction of a plant temperature 

 "zero," into the study. This zero was the minimum temperature at which 

 plants would grow, and variously placed at o3° , S0° , 1/2° , 50° and even 

 OJf'^ F. These values were subtracted from the temperature readings 

 before determining the sums for the season. This metiiod presumed that 

 the effectiveness of air temperature in promoting plant growth was 

 directly proportional to the number of degrees above the minimum 

 temperature for jjlant development. The temperature most frequently 

 used as the zero for plant growth seems to have been i2" F., in which 

 case a mean daily temperature of 50 F. would be given a weight of 

 eight. 



Largely to demonstrate the futility of this method wliich has been 

 used so extensively and is still considered efficient by some, I have taken 

 tlie splendid phenological records of Afr. Thomas Mikesell^ and his 

 temperature readings at Wauseon, Ohio, and compiled tables of the 

 sums of temperature readings in the life liistory of the late Crawford 

 peach, for the years 1883 to 1912, inclusive, shown in Table I. Columns 

 I to 5, give, respectively, tlic tein))('ratiirt' summations above 1-2" 1"\ from 



