Grossenbacher—Radial Growth in Trees. 
37 
deprived of marked radial as well as elongation growth for sev¬ 
eral years, and the long-continued scarcity of food in the upper 
part of the top is said often to result in the dying back of the 
upper branches and thus gives rise to stag-horn effects. The 
length of time required for adjustment to the new environment 
is said to depend upon the extent of a tree’s leaf surface. The 
sprouts, which often arise on long bare trunks, are thought to 
be induced by the swaying action of the wind thus tending to 
develop a lower head. 
An enormous amount of data and calculations on the relation 
of the environment to radial growth and its distribution was also 
callected by Schwarz 71 and published as a monograph which in 
addition contains many very important observations on the life 
and seasonal historj^ of Pinus silvestris. It is noted that yearly 
radial growth as measured by the area of its cross section in¬ 
creases in trees until the age of about 20 to 30 years is reached, 
but under very favorable environmental conditions its growth 
may increase to the age of 100 years. His general conclusions 
regarding the wind in its relation to the distribution of radial 
growth are practically the same as those put forth by Schwen- 
dener and Metzger. Some instances are cited where the tops of 
trees had been broken off when about 30 years old and which had 
since grown about 60 years with lateral branches diverted to 
function as the main axis. In the region of curvature of the 
branch which assumed the functions of the main axis excentric- 
ity became very marked, with the greater radius on the under 
side. It is thought that the excessive pressure or weight on the 
under side was the stimulus to increased radial growth on that 
side. In one case, in which the curvature induced had been such 
as to exert the greater pressure on the upper side in one place, 
it was found that this upper side had the greater radius. Many 
measurements on vertical stems also showed a greater radius on 
the leeward side in regard to the prevailing wind. By tying a 
young pine tree in a bent position excessive growth resulted on 
the compressed side, i. e. it seems that a fixed, bent position ex¬ 
erts the same influences on radial growth as the discontinuous 
pressure due to wind swaying. Other measurements on slightly 
inclined trees also showed a greater radius on the side toward 
which the trees inclined. It is held that relative amounts of 
1. c. 
71 
