July, 1923 ] 
CURTIS — EFFECT OF RINGING A STEM 
363 
absorptive ability would not be lost through death or starvation. All ring 
wounds were covered at the time of ringing with warm paraffin. This pre¬ 
caution was necessary, since otherwise the parts above the ring would often 
wither. Paraffin instead of vaseline or grafting wax was used, for in pre¬ 
vious tests it was found that vaseline was often injurious to stems and that 
grafting wax was injurious or less easily applied. Immediately after ring¬ 
ing, nitrogen as sodium nitrate was added to the soil. In a few cases 
calcium nitrate, calcium chloride, and sodium chloride were also used. 
In every case the areas of the leaves, as well as the dry weights, were 
determined. The areas were determined by the use of a planimeter, and 
readings were determined to tenths of a square inch. With small leaves, 
like those of Ligustrurn, it was found that the error in measurement was 
greater than that for the larger leaves. In most cases, each lot of leaves 
of known area was divided into halves or fourths for analysis, one of the 
halves or two of the fourths commonly being reserved for ash determina¬ 
tion. Total nitrogen was determined by the Gunning method as modified 
to include nitrate nitrogen. The ash was obtained by combustion of the 
material in an electric furnace at a low red heat. 
Since peach trees (Prunus persica Sieb. and Zucc.) distinctly show a 
deficiency of nitrogen by the formation of yellowish leaves and by their 
slow growth, and since they respond so readily to nitrate applications, 
experiments were first tried with these. In all the experiments with peach 
trees, branches one to three centimeters in diameter on young trees were 
selected. In ringing, bands of bark from one to two centimeters in width 
were removed. 
In the first series, the branches were ringed in May just before the 
leaves were formed. At the time of collecting the leaves, those from the 
ringed branches were distinctly smaller; they were thick and stiff, yellow¬ 
ish in color tinged with red, and the younger leaves at the tip of the stem 
were very much curled. The check leaves from the unringed stem, on the 
other hand, were larger, thin and pliable, dark green, and not curled. By 
the end of the season the unringed branches had produced shoots several 
times as large as those of the ringed branches. For tree number 1, the 
three largest shoots developing from buds near the apex of the ringed 
branch averaged only 31 cm. in length. They had no side branches and 
only 50 leaves, while the three largest shoots on the unringed branch aver¬ 
aged 149 cm. in length. In addition, the check branches produced from 
22 to 25 lateral twigs. These secondary twigs of the check were from 8 
to 30 cm. long, and the total number of leaves was somewhat over 1,200. 
From observations of the color and texture, it would appear as if the 
ring had checked growth by preventing the upward movement of nitrogen. 
It is possible, however, that the check in growth and the color of the leaves, 
as well as their texture, resulted from an excess of carbohydrates in those 
parts above the ring rather than from a deficiency of nitrogen. The results 
of analyses for the nitrogen and ash contents of these leaves are presented 
in table 1. 
