Vermont watchman and State journal. [volume] (Montpelier, Vt.) 1836-1883, 1882-03-08
Sap Flow and Its Cause.

Sap Flow and It's Cause.
WATERBURY, CENTER, Vt, March 6, 1882
Mr. Editor No one knows 1t ALL The study
Of Nature is interesting and instructive to all
thoughtful students. When we see cause we
wish to search out the effect When we notice
effects we trace back in search OF the cause
The thinker knows there is sure connection,
and the possibility Of discovering it stimulates
him in the search and final discovery. We never
can know too much of Natures ways of doing
things, and Of her laws. As Nature never de-
ceives, and is ever honest and true so we are en-
couraged to press on in our investigations. In
the study OF men and books, we are liable to get
incorrect replies, but whoever consults Nature
by observation or experiment Is sure OF a reply,
and that a correct one. With this incentive to
study, the student Is sure Of ultimate success In
gathering and storing up ideas, thoughts, facts,
conclusions, results, ETC., thus adding to his
store of accommodating knowledge which cannot
fail to be source Of pleasure and profit inteec-
tually and financially. Natures field of study is
immense, there is room for all no one can occupy
the whole field. He who studies nature, as
whole, will never become an expert in any one
branch, but he who makes speciality of any one
and so be more apt to know all that can be learned
on that subject. While the astronomer may be
pushing his Investigations in the heavenly world,
the starry and planetary systems, the geologist s
content with the study OF one planet-our earth.
As the field Of the animal physiology may be oc-
cupied by one individual the field of vegetable
physiology may be occupied by another. Each
may become an expert in his own field. He who
studies plants whole will be less apt to be-
come an adept than he who makes speciality
OF any one plant.
While Professor Clark has made the general
subject of sap-fow from all sap-fowing trees a
specially, no one has, to my knowledge, made
speciality Of the study of sap-how in the sugar
maple. In my earliest experience in tapping
maple trees, looked upon the dripping sap in
wonder and establishment. With an incision and
conditions favorable sap-fow is a fact, but the
cause is not so obvious. The incsion is not the
cause, but, more properly, it is occasion for its
flow. Its flow cannot be due to its standing on
pressure. Sap or water that stands on its own
pressure must be fed, SO as to observe the law OF
gravity, or in other words it must be hydrostatic
water, but no such water is found in tree
Again, did sap stand on its own pressure, and
were 1t free from all other PRESSURE 1t could
never rise lin tube outside OF the tree) higher
than the top of the tree, but it is found by actual
trial in some to rise higher than the topmost
branches by several inches tree contains
microscopic water, air and certain gases. In a
continuous cold and unchanging winter these
contents Of the tree remain nearly at rest varying
only with the Temperature, while in an open
winter the tree Tor its contents) is more or less
antiva This nd tho ~ tba
contract by cold and expand by heat and 80 the
volume of each is changed and varied by chan
ging temperatures. In freeze the contents of
the cells contract, the tendency of which is to
form vacuum which induces suction instead OF
PRESSURE and so sap ceases to flow. In this con-
dtion, II hollow tube be inserted into a tree
filled with water it will be found that the water
is settling-passng into the tree showing suction
But this suction is not through the roots, as most
people think, but it is through the incision and
the whole surface OF the tree above the ground
In the morning the rises the tree Is rising in
temperature, the air and gases in the tree are ex-
banding and pressure is the result and the sap be-
gins to flow. Pressure then is the cause OF sap-how
The warmer the trunk of the tree, the greater Is
the expansion, the harder is the pressure, and the
more rapid is the flow of sap. Some authors and
experimenters think that in freeze the sap is
driven In towards the center OF the tree, then, as
the temperature OF the tree rises again, it rushes
back, and sap-fow is the result. Were this theory
true, the sap from circumference to center would
be homogeneous in its nature; but by careful test
experiments find that there are as many grades
OF sap from circumference to CENTER there are
rings or zones of yearly growth II given tree
is one hundred years old, then there are one hun
dred varieties of sap varying in three respects viz
color, taste, and specific gravity Whoever will
be to the trouble to bore a tree six inches deep
and arrange as to catch the first two inches in
one tub, and the second two inches in another
tub, and the third two inches in still another tub,
will find three saps varying as above stated in
these three respects; and the variation lin only
two inches) will be so apparent that no two per-
sons can fail TO be agreed in the variation. For
this reason and others that will not now stop
to mention, am obliged to dissent from this in
ternal movement theory. do not think the cells
contract, but their contents do. The contents
most certainly contract by cold, thus producing a
vacuum in all the cells of which lin the maple),
says Dr. Cutting, there are sin every cubic inch,
one hundred millions of cells of the various it's
sues. The average diameter Of plant cells is usu-
ally less than one four hundredth Of an inch"
Now, then, II the cells themselves do not con.
tract and expand but simply their contents, thus
producing one hundred millions OF vacuums in
every cubic inch, there must be an inflow OF va
por OF water to fill the vacuums, as 1t is said that
nature abhors a vacuum. These additions must
come from or through the roots, or 1t must enter
through the whole surface Of the tree above the
ground, from the atmosphere That the roots do
not absorb in the winter and early spring is evil
dent from several considerations, viz; First often
the ground is frozen to the depth OF two or three
feet and of course section OF the tree TO the
same depth, especially in open land where the
trees are scattering and standing on knobs and in
exposed situations, thus cutting off all commun
cation from the deeper roots which reach below
frost, and the body of the tree. Second, The
temperature is too low for absorption. Third, At
this the tree il not in leaf and hence there
be root action, because there is no leaf ac-
ton. From my standpoint root-absorption and
sap-how cannot take place simultaneously Root
action commences Its activity at the close OF its
winter repose when sap-flOw Is diminishing and
the buds are swelling. Root action is normal
but sap-dow is abnormal, therefore one cannot
supply the other hence the conclusion seems to
be inevitable that the sap, when the tree il not in
leaf, must come from the atmosphere in the form
OF vapor OF water Now, then, let us see II we
can discover the law by which this is accomplished
The bark OF the tree is non-conductor OF heat
80 the heat is measuraby radated, and as night
comes on the tree becomes several degrees cooler
than the atmosphere, thus making III eItree con-
denser like pitcher OF ce-water in the summer
with this difference the pitcher being n'n-porous.
the yapor OF water collected from the atmosphere
increases, forming hydrostatic water, while the
tree is porous and so abeorbs the yapor of water
and 1t enters the tree as Microscopic water and
fills the vacuums made by contraction, so that as
the tree heats up with the morning sun, suction,
caused by the expansion, ceases, and pressure is
the result, and sap flows again.
TIMOTHY WHEELER.
QUEEN VICTORIA is not without womanly SUI
perstitions She Is said to be averse to having
her son Leopold marry in May because that was
the month in which the poor young Princess Char
lOlta waa ssaxdad IN King Iaonnla