May, 1914.] 
Starch Reserve in Birch and Maple. 
3 I 9 
small tree on the south bank of “Mirror Lake,” while producing 
a sap of lowest concentration, yielded more sugar per hour than 
any other of the maples. Under the varied conditions of the 
experiment, all maples produced a clear creamy white sugar 
in which little difference in taste was noticed, although the silver 
maple, No. 4, was in flower at the time. The average concentra¬ 
tion of sugar in the sap for the maples was 2.2 %. These results, 
together with those of Professor Jones, make it probable that the 
Bonn Text Book is in error in rating the average % for the North 
American maple at of 1%. The average yield of maple sugar 
per hour was 4 grams. 
At the close of the sap run, April 10, there was almost no corro¬ 
sion of the starch granules in any of the woody tissues of the sugar 
maple. There was little starch in any of the tissues of the bark 
of the young twigs; but starch was still abundant in the same tis¬ 
sues of the root. On April 24, the flowers had fairly opened, and 
were so numerous as to give the crown of the tree a general green 
color. Starch had been used from the branches examined, which 
showed less than 9 annual rings of wood. 
In summary, it may be stated that, previous to bud growth, 
little starch had been used, the most pronounced changes being 
confined to the bark of the stem. While buds were swelling, the 
starch was used from twigs showing less than 3 annual rings of 
wood. By the time flowers were fully formed, starch had been 
used from all portions of the stem showing less than 9 annual rings 
of wood. In other words, starch has been used first from the 1- 
year old twigs; then, from those portions of the branch showing 
two annual rings of wood; then, from portions showing 3 annual 
rings, and so on progressively down to that portion of the branch 
showing 10 years of wood. Beyond this, as in the root, no mark¬ 
ed changes have occurred as yet. 
I am indebeted to Mr. H. Udovitch, who has generously aided 
in collecting data in the flow of sap, and who has supplied the in¬ 
formation concerning the use made of the birch in Russia. 
EXPLANATION OF PLATE XV. 
Figure 1. Cross-section of 1-year old twig. 
Figure 2. Cross-section of root. 
u. m. uniseriate medullary ray. 
b. m. biseriate medullary ray. 
I. trachea. 
d. p. differentiated pith zone. 
p. undifferentiated pith cell. 
w. f wood fibre. 
w. p. wood partnehyma. 
b. p. bordered pit in section, 
j. p. simple pit in section. 
