The Barre daily times. (Barre, Vt.) 1897-1959, 1911-05-03
WHICH WAY DOES SAP FLowa
An Easily Constructed Gauge That Is
of Use to Sugarmakers.


Ask maple sugar workers which way
the maple juice flows; one viii answer,
"From the roots the second From the
branches and the third, Il do not
know" writes w. s. O. Russell OF Rut-
land county, VT, in the American Gull
tivator. The first two are guesses and
partly right. Many are like the third
person, who has never given il thought.
Sufficient for his purpose is the knowl-
edge that If the tree is punetured the
sap will flow.
The principle underlying the trans
mission OF sap from cell to cell is tech
nically termed osmosis. If two cells are
in contact, one OF which contains a fluid
less dense than the other, then the con-
tents OF the cell containing the less
dense fluid will soak or oniose into the
cell containing the more dense fluid
This has frequently been shown in the
laboratory by immersing a porous cup,
closed at the top and connected with
gauge, in distilled water in second
cup The first cup contains a dilute
solution Of saltpeter or sugar, After
little pure water will work its way
through the wall of the inner cup faster
than the sugar solution can work out
The result is an increase of pressure
in the inner cup which il measured by
the rise Of mercury in the gauge.
Plants and trees gather most of their
fluids in the same way. A tree is but
an infinite number of cells, more delicate
than the artificial ones of the expert
menter. with those near the circumfer-
ence in perfect condition. The myriad
roots are absorbing moisture, in fact,
gathering il so greedily that the fluid
is pushed upward from cell to cell with
irresistible force which fills the tree
70 saturation ON many days, and pres
sure is exerted which can be measured,
/ have devised simple gauge which
any boy can construct. Select a four
ounce bottle, with two-holed rubber
stopper to il, fill the bottle two-thirds
full of mercury, and pass through the
holes heavy.walled glass tubes, one OF
which is bent at right angles four inches
from the end and carrying a three
fourths inch one-hole rubber stopper to
be inserted tightly In tree. The tube
from the tree to the bottle should be
two feet long, and the other should be
continued up the tree five feet by join
ing the glass tubing end TO end with
short, stout rubber tubing. Set the
gauge thus made on block, and strong
" wire the stopper down to the block,
and wire the other stopper into the
tree
The tendency of the sap to escape
from the wounded tree exerts down
ward pressure on the mercury, and the
consequent rise of the mercury in the
long. open tube measures this force.
The gauge is a sap meter--it IS subject
to sudden and great changes of lever,
which correspond exactly with the vol
ume of flow of sap from the neighbor-
ing trees. A sudden and continued rise
of the mercury foreteils an immediate
flow of sap. Every sugarmaker should
fit one tree early in the season with
such gauge, as il will tell the time to
tap.
The tree undergoing examination by
nv botany class at this writing has
registered 30 inches of mercury. Since
mercury is 1896 times as heavy as wa
ter we win assume the density of sap
TO be one in the ealculationl, we have
| the following proportion by changing
inches to feet: x;2,666: 1885,, in
which equals s6246 feet. This shows
that the tendency OF sap in this tree "a
flow through the opening Is equal to the
pressure OF 36.246 feet of water. This
corresponds quite closely to the height
Of the tree and leads logically to the
inference that on q good sap day We
may regard tree as hollow cylinder
filed with sap; This conclusion is
strengthened by the reading of the gauge
placed many feet above the ground ii
the same tree. for the readings Of the
two conformed TO the law that pressure
in liquids varies directly As the depth
From two to four weeks hence The
birches viii transmit their sap. and tbs
flow Is much greater than in the maple
especially in the case Of the black and