I afterward found
that exactly fifteen days ago circumstances rendered necessary the
removal of the portion of the branch which hung over the path, 4 or 5
feet being still left on the tree. The water or sap was dropping fast
from the branch, at the rate of sixteen large drops per minute, each
drop twice or thrice the size of a "minim," and neither catkins nor
leaves had yet expanded. I decided that some interest would attach to a
determination both of the rate of flow of the fluid and of its chemical
composition, especially at such a stage of the tree's life.
A bottle was at once so suspended beneath the wound as to catch the
whole of the exuding sap. It caught nearly 5 fluid ounces between eight
and nine o'clock. During the succeeding eleven hours of the night 44
fluid ounces were collected, an average of 4 ounces per hour. From 8:15
to 9:15 this morning, very nearly 7 ounces were obtained. From 9:15
to 10:15, with bright sunshine, 8 ounces. From 10:15 until 8:15 this
evening the hourly record kept by my son Harvey shows that the amount
during that time has slowly diminished from 8 to a little below 7 ounces
per hour. Apparently the flow is faster in sunshine than in shade, and
by day than by night.
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