332 



W. A. CANNON 



TABLE 7 



* Average of 12 hours. 



t This and subsequent rates are average of 3 hours. 



suggest a rational basis for agreement. The writers referred 

 to are Leitch^ and Lehenbauer' to whose work the reader is 

 referred for literature covering the subject. Leitch used the 

 roots of seedling Pisum and Lehenbauer the shoots of seedling 

 maize. The third day after germination Leitch selected for 

 study plants wdth roots about 15 mm. long and such as were 

 the most uniform. This was at, or after the time of most active 

 growth, and not before this time. Although Lehen]bauer did 

 not manipulate his experiments with direct reference to. the 

 "grand period," his procedure was uniform and it may have 

 had a fairly constant reference to such period. The growth of 

 shoots which were 10 to 12 mm. in length was studied. Ab- 

 normal individuals were eliminated. The duration period of 

 the experiments was 39 hours or less. These workers obtained, 

 results differing somewhat in character. Leitch found among 

 other things a fairly constant growth rate for any temperature, 

 while, on the other hand, Lehenbauer found the rate to accel- 



1 Some experiments on the influence of temperature on the rate of growth of 

 Pisum sativum. Ann. Bot., 30: 25, 1916. 



- Growth of maize seedlings in relation tc temperature. Phys. Researches, 

 1: 247, 1914. 



