Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1874-01-29
Circulation Of Sap.

Extract from Pres Clark's (of the Mass
achusett. Agricultural College,) address at
the meeting of the State Board of Agri-
culture:
In regard to the circumstances which
affect the flow of sap from the sugar maple
the following results have been arrived at
A careful comparison of the daily weight
of sap from several trees with the meteor
illogical observations of the same period
conclusively prove that while the general
flow corresponds with the season, rising
to Il maximum and then declining yet the
4 ii V and hourly flow varies with the
weather. The most unf,vOrable weather
is that which is either steadily and severely
cold or iforlnly wa IN and foggy. while
warm ut midday, but preceded by free1
ing nights Such virie les of temperature
us affect the flow of III pie sap are most
likely to occur when the ground is covered
with low, because the heat of the sun
during the d,y cannot then accumulate to
moderate the cooling influence of the night.
The most probab explain ttion of these
tltera ions. appears to be ,at the outer
tissues of the tree are partially emptlc,l OF
their contents by the contracting in iuence
of cold, the sap being driven into the heart
wood of the trunk and large roots. Mean
while absorption goes on us usual under
ground, and thus, when relief is afforded
by the heat of the sun. the sap rushes back
to the surface and flows abundantly.
Experiments also prove that spring sap
enters and fills the heart wood rs well us
the albumen. Trees tapped on the north
side yield twice us much sap us those tap
81,
weeks longer. Sap flows most freely
within twelve feet of the earth, and flows
from both ends of n cut root. The average
Weld of ordinary trees in sugar orchard
is sixty pounds of sap and two pounds OF
su gar. but a tree in Leverett is reported to
have produced 400 pounds of sap-prob-
ably about 40 pounds ofsugar. There is
no good evidence that the bleeding of trees
or vines has any appreciate effect upon
their growth or health.
1t only remains to state in II few words
some of the surprising results obtained by
the application ofmercurial gauges to the
SUGAR maple. the black birch and the
grape vine. Observations We're made on
one or more gauges several times daily
and occasionally every hour of the day and
nioht. from the first Of April to the Goth of
July.
A gauge was attached to y sugar maple
March Slst which was three days after the
maximum flow of sap for this species, so
that further observations are required
earlier in the season to complete the record
and determine with certainty the maxi
mum pressure which it exhibits in spring.
OF the record made the following facts
are specially interesting. First. the mer-
curry was subject to constant and singular
oscil ations, standing usually in the morning
below zero 50 that there was indicated a
powerful suction into the tree, and rising
rapidly with the sun until the force indca-
ted was sufficient to sustain column of
matter many feet in height. Thus at A.
NJ, April . ST. there was suction into the
tree sufficient to raise a column of water
Is. 80 feet As soon us the morning sun
shone upon the tree the mercury suddenly
began 10 rise, SO that at 8 is A. NJ, the
pressure outward was enough TO sustain
a column of water 1917 feet in height, a
change represented by more than A feet
of IN Utter. On the morning of April 22d
the change was still greater, requiring Tor
its representation AZ ~ feet of water.
These extraordinary fluetu tons were not
attended bv any peculiar state of the
NctlurI, anu HtplClVN l"Si'O 49, - oOIoi'
there were any Indications of growth To be
lrtecte in the In Is. These observa ions
are quite nev AMI rs Y wholly inexpli-
cube, bat will receive further attention
another spring.
The III tXimum pressure OF the sap for
The season WAS observed at 10 A. NJ. tpril
18th, and WAS equal to sustaining u column
ot water 3l.73 feet high. This was ;tn
excellent sap day considering the latenes>
of the season There WAS noticed Il gen
eral correspondence b tween the flow of
sap in othrc ma. les ahd the pressure on
the gauge
Afer April 10Th the mercury remained
co sttntlv below zero day and night.
During the month of May the was a
uniform suction equal tn about eight feet
Of water. and the unaccounttble feature OF
this fact j. that, though apparently pro
luced bv eXhaiation from the expanding
leaves il remained the same, day and
night for several weeks. In June, the
suction gradually lessened and finally dis
appeared. the mere ry stlnding steadily
IT zero The fact that cXhalalion from th,
leaves of growing plants would cause Il
suction capable of holding up several feet
of water was discovered by IIales. but has
no apparent come ton with these phe-
nomrna, N L. Homestead.