July, 1923] CURTIS — EFFECT OF RINGING A STEM 379 
per gram of bark in the ringed stems with low carbohydrate (no. 2). This 
is probably in part accounted for by the distinctly low'er dry weight of 
the bark of these stems, as there was no phloem connection with a carbo¬ 
hydrate supply. In no. 2, the dry weights of the bark samples were re¬ 
duced on the average by 17 percent, the total nitrogen was reduced by 
25 percent, and the nitrogen per gram by 11 percent. In no. 3, the dry 
weights of the bark were increased on the average by 50 percent, the total 
nitrogen was increased about 2 percent, and the nitrogen per gram was 
reduced by 22 percent. 
Considering the twig as a whole, the rings at the bases of the defoliated 
parts distinctly reduced both their total nitrogen content as well as that per 
gram of dry weight. 
Discussion 
The results recorded in this paper are not in accord with those reported 
by Hibino (1917), who found that the proteins and ash contents of twigs 
of Cornus controversa were higher in the twigs ringed to the cambium than 
in the checks. Those ringed through the sapwood showed still higher 
protein, but lower ash than the checks. The protein contents in percent¬ 
ages of dry weight were 5.75, 6.31, and 7.81 respectively, in the check twig, 
in that ringed to the cambium, and in that ringed through the sapwood. 
The ash contents were, respectively, 1.45, 1.75, and 1.32. Evidently but 
very few twigs were analyzed, and since comparisons were made between 
different individuals, and since their composition was not known at the 
beginning of the experiment, the final differences may have been due to 
individual differences existing from the beginning. As discussed in con¬ 
nection with table 7, I have found the nitrogen contents of stems of privet to 
vary much more than those of leaves. Stems from similar plants were 
commonly found to vary in nitrogen content between 8 percent and 10 
percent, and extremes were found with 6.39 percent and 14.96 percent 
nitrogen, a variation of over 100 percent. 
When it was found that some nitrogen evidently passes a ring, as indi¬ 
cated in table 3, it seemed possible that on long standing a ringed stem 
might accumulate more nitrogen than a normal stem, since probably little 
or none of that passing a ring is ever carried back. The stems in Hibino’s 
experiments had been ringed in July and were sampled in January. The 
data presented in table 2, however, indicate that leaves from a stem that 
had been ringed over a year may still have a lower nitrogen content. 
Combes (1912) has reported ash analyses of leaves from ringed and 
normal stems of various woody plants. Expressing the ash as percentage 
of dry weight, the leaves from the ringed stem had lower ash contents 
in every case, and when expressed as percentage of fresh weight, all but two 
of the seventeen showed lower ash contents. When expressed as total 
ash or as ash per leaf, with the exception of Pinus excelsa, which in every 
