H. S. REED 



551 



The Juglans regia trees were measured from June 5 to October 22. 

 The data afforded by these measurements are shown in Table 11. 

 The average length of their growing season was 116 days from June 

 5, which means that the average tree ceased to grow on September 

 28, though it was October 22 before all trees ceased to increase in 

 height. 



We may proceed to examine the growth rate of these trees by a 

 method which has elucidated many problems in the domain of physi- 

 cal chemistry. 

 140 



70 



Time in days 



Fig. 3. Growth rate of Juglans nigra trees showing two cycles. Curves show 

 computed values; points within circles show observed mean height at various 

 intervals. AOB are axes for the upper curve. 



Reference to the graph representing the mean height of the trees 

 at successive intervals shows that the curve consists of two rather 

 distinct parts, indicating that the growth period comprised in these 

 records consisted of two cycles. The curve rises rather regularly 

 from the 1st to the 62nd day, then rises more steeply to near the 110th 

 day, when it takes a nearly horizontal position. A few simple cal- 

 culations will show that the growth curve does not follow the path of 

 a single autocatalytic reaction. 



