378 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
in each set was ringed only at the base of the defoliated part so as to allow 
the carbohydrate to move down from the upper leaves. Though no meas¬ 
urements were made, it was assumed that transpiration from these stems 
would approximate that from stems I and 2. 
When the stems were cut they were tested with iodin to ascertain any 
evident differences in their starch contents. In the check (no. 1) starch 
was abundant in the xylem. In no. 2 no trace of starch could be detected, 
and in no. 3 starch was evidently somewhat more abundant than in no. 1. 
Averages of the data obtained are presented in table 7. 
As indicated by the table, the bark and wood were analyzed separately. 
The volume of each twig was calculated from the length and the diameters 
at each end. Analyses of the wood showed that the ringing at the base 
of the defoliated part had resulted in a lower nitrogen content of that part 
whether measured as total nitrogen per stem, as nitrogen per gram of dry 
weight, or as nitrogen per unit of volume. This was true in each of the 
twelve sets with but two exceptions. One of the exceptions, in fact, adds 
weight to the evidence, for in this one twig the ring had healed over. The 
data for this one twig are not included in the averages. In the other excep¬ 
tion, the difference was slight and probably due to inaccurately paired 
twigs. It should be mentioned in this connection that these twigs showed 
much greater individual variations than did the leaves. The nitrogen 
contents of the xylem, for example, expressed as percentages of dry weight, 
varied in the check twigs from a minimum of 4.21 percent to a maximum 
of 9.95 percent. For each set of three twigs, however, care was taken 
to select those similar in position, size, and color of leaves, and, with the 
exception just mentioned, the check in each set of three always had the 
higher nitrogen content. 
The data also show that the effect of ringing on the nitrogen content 
of the wood above the ring is independent of its effect on the carbohydrate 
content. In one treatment (no. 2) the carbohydrate content was much 
reduced by the ring, as evidenced by the tests for starch and by the dry 
weights. In the other treatment (no. 3) it has increased the carbohydrate 
content as indicated by the same tests, yet in both cases the nitrogen con¬ 
tent is distinctly reduced. In no. 2, the dry weight of the wood was re¬ 
duced on the average by about 23 percent, the total nitrogen 46 percent, 
and the nitrogen per gram 30 percent. In no. 3, the dry weight was in¬ 
creased 62 percent, the total nitrogen was reduced 28 percent, and the 
nitrogen per gram was reduced 58 percent. 
Analyses of the bark show that the rings at the bases of the defoliated 
stems resulted in a distinct reduction of the nitrogen in those which had 
a low carbohydrate content, but had practically no influence on those 
which had excess carbohydrate. The amount of nitrogen per gram of 
material seems to be clearly reduced. In two instances, not including 
the stem which had healed, there was a slightly higher amount of nitrogen 
