162 ILLINOIS STATE ACADEMY OF SCIENCE 



Variations in lengths of blooming periods such as those 

 cited are of common occurrence and cannot be caused by 

 spring weather conditions alone ; by their marked irregu- 

 larities they suggest that the individual rather than the 

 variety must be the basis from which performance is 

 considered. Trees of one variety growing together in 

 the same row do not act alike ; one starts earlier, pushes 

 stronger, and completes its period of bloom in less time 

 than does its neighbor. It is said of such a tree that it 

 was in better condition than the other, had more vigor 

 and was thus enabled to outclass its neighbor ; this is true, 

 but when the question is asked, Why was the tree in bet- 

 ter condition and possessed of greater vigor? the answer 

 is not immediately forthcoming. 



The tree of greater vigor may be constitutionally better 

 than its neighbor ; it may have had access to better food 

 supply; it may have recovered more completely from a 

 fruiting effort ; it may have escaped a parasite that dam- 

 aged its neighbor ; any of these or possible other causes, 

 singly or in combination, may have operated to bring 

 about the recorded differences, leaving no evidence of op- 

 eration that is apparent at the time bloom record is made. 



