294 
OTIS F. CURTIS 
The data obtained from ringing dormant stems show that, when the 
ring is no further back from the growing tip than that part of the branch 
from 5 to 15 years old or from one to five centimeters in diameter, the growth 
may be practically as extensive as when no ring is made. When the growth 
was somewhat lessened by ringing, it may have been due, not to a lack 
of food, but to a deficiency of water, as the ring, of course, prevented the 
formation of a new layer of xylem. Furthermore, although the rate of 
starch loss was more rapid when the ring was near the tip, indicating more 
complete usage of stored food, yet the rate of starch loss when the ring was 
in the older wood was approximately the same as from a normal stem. 
These results indicate that normally very little food is withdrawn and 
carried up from the main trunk or roots to be used in shoot growth. It 
would seem therefore that, especially in older trees, the food in the branches 
is more than sufficient to initiate shoot growth, and that, since much of the 
food necessary for continued growth may be produced by the young leaves, 
there may be no tendency to draw upon that food stored in the roots. 
Furthermore, the fact that a cutting no longer than six inches may produce 
a short shoot with leaves and also a callus and roots, when no food can be 
obtained from storage organs outside that small bit of stem, would indicate 
that a shoot on a large branch need not draw on food stored at great dis- 
tances, as from the trunk or roots. 
There seems to be little foundation for the statement (Butler, 191 7) 
that the carbohydrate stored in the young root tip is digested in the spring 
and carried up the trunk to the stems for shoot formation. It seems more 
probable that the roots themselves use nearly all, if not quite all, of the 
foods stored in them. When one considers that root growth probably 
commences earlier in the spring than shoot growth and may also continue 
later in the fall; that at no time can roots produce their own foods, as can 
the shoots as soon as a few leaves form; and that the tree roots probably 
store a smaller mass of food than do the tops, it is then difficult to see how 
food from the roots can be of very great d.id in the shoot formation of a tree. 
Summary 
Facts commonly considered as proving that the food which is stored in 
the roots and lower trunks of many trees is carried up to be used in shoot 
formation cannot be considered as actually proving such upward movement. 
When a ring is made on that part of a stem from 5 to 15 or more years 
old or from one to four or more centimeters in diameter, the growth above 
the ring approximates that of a normal stem, which fact indicates that up- 
ward movement of food from points below the ring is not essential. 
When shoot growth is well started, much of the food used for continued 
growth may be produced by the leaves of that shoot, which fact indicates 
that considerable growth may take place when but little stored food is 
available. 
