Grossenbacher—Radial Growth in Trees. 
43 
actual needs. On the other hand from the work of both Jost 
and Lutz it is also evident that the presence of food, transpira¬ 
tion current and suitable environment alone do not result in 
radial growth when no developing buds or shoots are present; 
i. e., cambial activity seems somehow to be dependent upon 
elongation growth or some enzyme activated or produced by it. 
The determinations by Fabricius, however, have made it ap¬ 
parent that the distribution of reserve food in tree-trunks seems 
to be in accordance with some unknown law, which brings about 
maxima and minima of food storage in more or less definitely 
alternating regions. The marked differences in the amounts of 
reserve food in the regions of maxima and minima could not be 
attributed to differences in the storage capacity of the regions 
for such differences would have been noted, nor to the distribu¬ 
tion of the branches because the wave-like succession of maxima 
and minima also occurred and it was usually most marked on 
the branchless portion of trunks. There is some indirect evi¬ 
dence to be had from the cited papers which tends to show that 
the places of the inception and longest duration of radial growth 
in a general way are the places of maximum food storage, and 
therefore gives support to Mer’s 86 contention to the effect that 
radial growth begins first where most food is stored and is most 
active and persists longest in such regions. The Schwendener- 
Metzger-Schwarz hypothesis suggests another way out of the 
difficulty by its assumption that wind action is responsible for 
the distribution of both metabolized food and radial growth. 
But we cannot admit the far-reaching claim of these investiga¬ 
tors that wind and gravity are the only formative factors con¬ 
cerned in the distribution of radial growth especially since light 
and transpiration have been shown to be powerful formative 
agents. 
OBSERVATIONS ON THE DISTRIBUTION OF LATE RADIAL GROWTH ON 
FRUIT TREES. 
While studying crown-rot of fruit trees during a series of 
years, I found that the initial bark injuries which afterwards 
result in the disease usually occurred in places at the base of 
86 Mer, E. Sur les causes de variation de la densite’ des bois. Bui. 
Soc. Bot. France. 39: 95-105. 1892. 
