Ii6 
OTIS F. CURTIS 
Below the lower ring: There were traces of starch in the pith. 
Upper part of upper ring: There was no trace of starch. 
Middle part of upper ring: There were traces of starch in the pith and 
in some of the medullary ray cells. 
Lower part of upper ring: Starch was abundant in pith and medullary 
rays, similar to that between rings. 
Check: There were traces of starch in the pith cells in the regions corre- 
sponding to those listed above. 
In the other stem tested at the same time the results were practically 
the same. There was more starch in the check, however, which showed very 
distinct traces in the pith and very slight traces in the medullary rays and 
cortex. In both stems the results were striking. When the sections stained 
with iodine were held against white paper and observed from across the 
room, the sections from between rings appeared almost black and the others 
practically colorless. These results indicate that there is practically no 
longitudinal transfer of carbohydrates through the xylem. 
A similar experiment in double ringing was performed with several 
species of Crataegus. Stems were ringed April 6 and examined May 17. 
All showed results similar to those obtained with Ostrya; that is, in all 
cases starch had disappeared above the upper ring, was abundant between 
the rings, and was present in moderate amounts below the lower ring and 
in the check stems. Between the rings, starch was very abundant in the 
primary xylem and medullary rays; but the results were not as striking 
as those obtained with Ostrya, for the stem at no time contained as much 
starch in the pith and therefore did not appear as dark when stained with 
iodine. 
A number of stems of Acer saccharum ranging in diameter from 4.5 mm. 
to 24.3 mm. were double-ringed on April 6 and 7. The distances between 
the rings ranged from 15 cm. to 107 cm. At the time of ringing most of 
the stems were bleeding freely. A number of the stems were cut between 
May 6 and May 19. In all cases starch was completely or almost com- 
pletely absent above the upper ring, very abundant between rings and nearly 
absent to fairly abundant below the lower ring, depending on the time of 
cutting and the position on the tree. The data obtained from one such 
stem are recorded below and in table 12. This branch showed 15 annual 
rings at the lower ring; it was 24.5 mm. in diameter at this point, which was 
situated 16 cm. from the main trunk. At the level of the second ring, which 
was 107 cm. from the first, the diameter of the branch was 20.2 mm. The 
check branch was not perfectly matched but was somewhat smaller than 
the ringed one. The diameter at its base was 22.3 mm. 
Above the upper ring: There was no starch in any part except in a few 
scattering cells of the primary xylem. 
Between the two rings: Starch was very abundant in the primary xylem 
and the medullary rays. 
