460 BOTANICAL GAZETTE [JUNE 
largely utilized in leaf and also in blossom formation, when the 
latter precedes leaf formation. 
The most interesting fundamental principle of growth exhibited 
by the records obtained from the box elder and blue spruce trees 
is that growth evidently does not begin in deciduous hardwood 
trees and in evergreen conifers at the same time. These observa- 
tions in general agree with the conclusions of KNupson. It would 
appear reasonable to assume that diameter growth proper, as 
distinguished from any preliminary swelling of the tissues which 
might occur, may be delayed until the new leaves are sufficiently 
developed to elaborate the supply of food needed for the rapid 
growth which takes place. The supply of stored food which is 
present in the spring is largely consumed in the formation and 
development of the new crop of leaves to a stage when they can 
supply the quantity of elaborated food necessary for the growth 
processes. On the other hand, the evergreen conifers, having an: 
adequate amount of living leaf tissue, are capable of supplying 
the requisite materials for growth as soon as growing temperatures 
are reached in the spring. In other words, the inception of 
diameter growth in evergreen conifers may practically be simul- 
taneous with the bursting of the buds, while in deciduous-leaved 
hardwoods it may be delayed until the new leaves have attained a 
sufficient size to manufacture their own food. 
It will be noted that the march of diameter growth is inter- 
rupted by rest periods of rather short duration. These rest periods 
are held to be essential for the maintenance of the proper health 
and optimum efficiency of the vital activities of the tree. 
Figs. 2 and 3 combined outline the seasonal course of diameter 
growth as follows. It begins slowly, and after a variable period 
increases rapidly by leaps and bounds, alternating with rest 
periods, until a maximum rate is attained; after a short time it 
gradually decreases to a minimum, and then ceases altogether, 
when the usual alternate shrinkage and expansion (due to the 
changes in temperature and moisture conditions of the tree trunk) 
are exhibited. 
Aside from the scientific consideration of the fundamental 
principles of growth, the use of such an instrument as the dendro- 
