The Vermont watchman. [volume] (Montpelier, Vt.) 1883-1911, 1885-06-03
Professor Clark on Sap Circulation.

AS Mr.. Wheeler, both in his answer
to H. A. in another column and in pre-
vious articles, has referred to the exper-
iments of Professor William S. Clark of
Massachusetts, on the circulation of the
sap in plants and trees, we have thought
it well to give what he has said on the
subject of maple sap in his own Ian
guage, as we find it in his lecture, which
is printed in the Massachusetts, Agricul-
tural Report for 1914, Part l., PIP.
159-205. This is a very memorable
paper, recording a remarkable series of
experiments, which threw great light
upon several important questions, and
perhaps solved some of them. But they
are confessedly incomplete, and to that
extent unsatisfactory. 1t cannot yet be
said that everything is known in regard
to sap circulation. Professor Clark says
in his Introductory remarks: "To SUI
perficial observer it might seem very
easy to investigate, with the aid of all
the appliances of modern science, such
apparently simple and familiar phenom-
ena as the termination of little
seed and the growth of common tree.
But the difficulties to be overcome are
so numerous and peculiar that real
progress in knowledge is exceedingly
Slow Professor Clark's first reference
to the sugar maple is as follows:
"The curious fact that the Indians
used to make maple sugar in November,
that good sap days may occur during
any time between the first of October
and the first of May, that the flow of
sap varies remarkably during the ordi-
nary sugar season according to the
weather, and that the percentage of
crystallizable cane sugar in the sap of
the same tree is also subject to eXtraor-
binary fluctuations in different years
and in different months of the same
season, render the sugar tree of North
America a species of peculiar interest
to an inquiring botanist."
Six mercurial gauges were made and
applied to as many maple trees. These
gauges were visited and their fuctua-
tons recorded with great care from
three to six times every twenty-four
hours during period of ninety days.
Professor Goessmann of the Agricultural
College took the specific gravity of a
large number of specimens of sap, and
applied chemical tests for the determine
ton of sugar and other ingredients.
water" says Professor Clark, &c in
the liquid form is wholly absorbed by
the rootlets, though watery vapor must
under some circumstances be imbibed
by other vegetable organs. Only a
small proportion, however, of the water
taken up by the roots is assimilated,
much the largest part being exhaled by
the leaves. 1t performs, nevertheless,
most valuable service as a common car
rier throughout the various parts of
plants both of those heterogeneous and
other substances absorbed in very di-
lutte solution from the soil, and of those
organic compounds formed within the
plant, and essential to its growth"
Regarding the movement of fluids
within the tree, which is called their
circulation he says:
"Many have said there is no
such thing as a general circulation of
sap; but no one doubts the fact of an
upward flow from the roots, and vast
exhalation of water from the foliage,
during the period when the vital forces
of the plant are active. 1t is also uni
versally admitted that the cells contain
ing chlorophyl (green coloring matter
of the leaves and young bark are the
organs in which the elements of the
carbohydrates (sugar, starch, gum,
wood) are combined, and from which,
therefore, they must pass by some
channel to all other parts of the plant
where either growth occurs, or such
substances are stored up for future
use. Whether the albuminoids Sub
stances containing nitrogen, most abun-
dant in the seeds) are formed also in
the cells of the leaves, or are the result
of combinations occurring in the cam.
blum (new wood layer between the
soluble carbohydrates and the ingredi.
ents of the ascending sap, is not Ger.
tain"
Professor Clark reviews the facts col.
lected by botanists for many years in
connection with tree-life and tree
growth, and concludes that the sol
water, or (" crude sap }" absorbed by the
roots, ascends to the leaves through tn,
" sap-wood that is, wood one o.
few years old-while the new materia
for the current years growth descend
beneath the bark, forming the " cam
blum" or soft, new-formed wood, which
is to constitute the outer layer of sap
wood of the next season. There is NJ
ground for believing that the circulation
of the sap of the sugar maple is differ
ent in any essential particular, or in thu
principle of its operation, from that o
any other tree. 1t may differ in details