Vermont watchman and State journal. [volume] (Montpelier, Vt.) 1836-1883, 1874-04-15
&grtoult ural.
Circulation of Sap.
uonl, isrsur.rrso AND VALUABLE EXPERIMENT

utanLY INTERESTING AND VALUABLE EXPERIMENTS.
President Clark, Of the Massachusetts
Agricultural College, has just completed a
series Of experiments in relation to the cir
culation of sap, throwing additional light
on the subject, and bringing out new and
important facts The degree or force Of
he upward pressure Of the sap, as well as
the force Of suction into the tree, we're
measured with great accuracy by means Of a
mercuria gauge. A s,op.cock was screwed
firmly into the sap wood Of the tree, and a
glass tube, previously bent in the form Of a
double siphon, was attached by means Of
couplings Of iron. The right end may be
extended and filed with mercury to any re.
qured height Any pressure Of the sap
drives the mercury down the middle tube
AMI up the right hand one and suction into
the tree reyerses the operation. When the
mercury stands level, there is no pressure
either way A scale accurately measures
the amount The whole is enclosed in o
box, which may be kept shut when not uu
der examination
The following are some Of the results OF
the experiments A gauge was attached to
to sugar maple on the 3lst Of March, or
three days after the maximum flow Of sap,
little too late EARLY in the morning Of
each day, there was suction Into the tree,
and on April 2l,t 10 was equal 10 q column
Of water 26 feet high A change com
menced as soon as the morning sun shone
on the tree, and the mercury began to rise,
50 that soon after eight o'clock A. W. it was
enough to sustain Isl feet ofwater, change
gilmore than A. feet. On the 22d Of April,
the change was more than Il feet OF water.
These changes occurred twelve days before
there was any indication Of growth de.
tected in the buds The maximum pressure,
April llth, was equal to sustaining col
umu Of water over 81 feet high. Thiswas an
excellent "sap day" After April %, the
mercury was constantly below zero day and
night-that is, there was constant suction
into the tree, aud during May the uniform
suction was about equal to eight feet Of wa
ter. Ia June it gradually lesscued and
finally disappeared mercury then
standing level or at zero
On the Goth of April, two gauges were
attached to a large black birch tree, the
lower one showing the enormous pressure OF
56.G5 feet Of water, and the upper one
26.7l differing almost precisely with the
difference in height one above the other.
When the upper gauge was raised II feet
higher, the pressure was II feet less n
gauge was then attached, on April 10th, to
the root of black birch, cut off or sep
arated from the tree, in cold, damp earth, a
foot below the surface and unaffected by
the warmth Of the atmosphere. 1t rose
constantly, with slight fluctuations, in four
days, until about noon Of the Both it stood
at the unequaed height Of 80 80 feet oil
water. This showed that the absorbing
power OF the living rootlets, without the
help attributed by some of cxhalation above
Utilization, contraction, capillarity, osmose,
&c, effected this wonderful elevation, and
| from these and other results President Clark
comes to the conclusion that it is affected
alone by the rHal energy Of the plant
which is in fact as reasonable in itself o.
e any mechanical or electrical or any Other
+ agency. II vital energy will cause an ami
y NAL to lift a hundred pounds weight 10y
. the force Of the wilD, we do not see why
! it may not be assigned as the lifting force il
this case.
To determine whether the sap would flow
. from the heart-wood Of the sugar maple,
piece Of sharpened gas-pipe was driven ST,
- inches into the tree. The flow was regua
o and long continued, but not so abundant a.