554 



THE NATURE OF THE GROWTH RATE 



time at which Juglans nigra began its second growth cycle. We do 

 not know whether Juglans regia had two growth cycles, but the pre- 

 sumption is in favor of such an hypothesis. 



Data such as these afford a new insight into certain phases of growth 

 in the organic world. They show that the growth rate of these or- 



TABLE IV. 

 Height of Juglans regia Trees. Comparison of Observed Values with Those Calcu- 



ganisms follows a course as definite and as predictable as that of a 

 chemical reaction. On the basis of pure chance we should not expect 

 often to find a group of indi\dduals which should follow a definite rate 

 of development more closely than the laws of random sampling would 

 require. 



The onset of dormancy in the two species of Juglans is worthy of 

 notice. It should be remembered that the two lots of trees grew in 

 adjoining rows in the nursery and received similar care as to irrigation, 



