BOOKS AND CURRENT LITERATURE 



Temperature and Crops. — It is certainly a step in advance when 

 meteorologists and climatologists can turn bone-dry weather data 

 into terms of practical value to the farmer and agriculturist. As long 

 as they are ignorant of the physiological processes going on in plants, 

 just so long will the data they collect be useless to the practical man. 

 At the present time, there are a few meterologists who have taken work 

 in plant physiology and ecology or have the broader view and are able 

 to interpret the weather records, but even these must discover some 

 other means by which their data can be made to mean something. 



D. A. Seeley in his article of 1917 on the Relation between Tempera- 

 ture and Crops^ has shown that. what we need more than mean annual, 

 monthly and daily temperatures, is a method of evaluating air tem- 

 perature in terms of its efficiency to meet the plant's thermal require- 

 ments. The temperature of the plant itself should be given more 

 consideration. Curves expressing plant growth rates and plant 

 temperatures show parallellisms more decided than other temperatures 

 observed, including maximum and mean temperatures and soil tem- 

 peratures. A test of the number of heat units required to cause a 

 cherry tree to blossom in the greenhouse as compared with the out- 

 doors shows remarkably close results when plant temperatures are 

 considered, but when air temperatures alone are considered there is a 

 wide variation. 



Mr. Seeley's latest article on The Length of the Growing Season in 

 Michigan^ shows how the period between the last spring frost and the 

 first autumn frost can be the limiting factor in crop production for 

 certain sections of Michigan. 



The records of frosts during the past thirty years or more for many 

 localities in the state have been studied and mathematical calculations 

 made to determine the risk from frost damage on certain dates. Tables 

 are given showing the dates in spring and autumn when there is an 



1 Seeley, D. A. Relation between temperature and crops. Monthly Weather 

 Review 45: 354-359. 1917. 



2 Seeley, D. A. The length of the growing season in Michigan. Mich. Acad. 

 Sci. Rept. 20. 1918. 



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