The Middlebury register. [volume] (Middlebury, Vt.) 1850-1882, 1879-05-09
CIRCULATION OF SAP.

eleventh annual report ofthe Massachu
sets Agricultural College for 1874
They will be found TO embody mucl
Interesting and useful information.
II was found that the great majorit,
of trees aid shrubs DO not bleed from
wounds in the wood at any season o
the year, and that the few species il
our latitude. which exhibit this phe
nomenon at all, do so to any considera
Bile extent only when deprived of tEeii
foliage. No peculiarity OF structure OF
habitat has yet been detected which ac
counts for the extraordinary differenct
among them. The soft and spong,
wood of the willow and elm, which of
ten grow in moist ground, might be
deemed specially suited to absorb and
pour forth water before the expansion
of their leaves or flowers in the spring
but the wood appears to contain no un-
usual amount of sap at that time. Ol
more than sixty species of trees and
shrubs tested by boring II lhree-quarlcr-
inch hole, usually to the depth of two
inches, into the sap-WOOd near the
5 earth, only those of the following gc-
ncra showed any tendency TO bleed, viz
= Bctu30, which includes the birches
, -Acer. the naples; IItis. the vine,
OflYo, the hornbcam; Jagidns, the
. wanuts. Tne genus Coryd. to which
r belong the hickories, sometimes, eX-
= udes very little, and possibly the
FdguS or beech, and Cd,pinUS, the hop
hornbean, may do the same. though no
opportunity has offered for testing them
satisfactorily. On the 10Th of March.
when the ground was still covered with
sno y, but Ircc from frost, fourteen spe-
cies of the common forest-trees were
tapped, aud nearly all those which were
subject to experiment. were tapped on
the 21 81 of April, and again on the Both
Of the same month.
II was found that each species of those
which flowed had its own time OF be-
ginning, when it seemed to awake
from its winters repose, that the flow
steadily increased in quantity and force.
as indicated by the weight of sap and
the pressure on q mercurial guage, un.
til it reached its maximum, and then
gradually declined; and that the com
position of the sap of the several species
differed remarkably, according to the
date of the flow, and especially the time
of its beginning. This singular period
| V,
stratcs that the absorption of water by
the rootlets is not caused by osmose, OF
any other mere physical force, but is
the result of the specific life which i'm
parts to every plant its distinctive char.
acteristics.
The sugar-maple begins to flow in
October, reaches its maximum about
the first of April, and ceases abeut the
first of May. The black birch begins to
flow the last of March, attains its maxi
mum the last of April, and stops about
the middle of May. The wild summer
grapevine commences about the first OF
May, arrives at its maximum of flow
and pressure about the 25th of May.
and ceases early in June. This differ
ence in the season of flowing is Of course
accompanied by corresponding varia-
ton in the temperature of the soil and
the atmosphere, and, very naturally
also, in the chemical condition of the
sap. Thus the principal ingredient OF
maple-sap is cane-sugar, that of birch
sap is grape-sugar, and that of vine-saI
is mucilage or gum.
These three carbohydrates, cane
sugar, grape-sugar and gum, arc doubt
less chiefly formed out of the starcl
which descended TO the root Ofthe pan'
and was deposited in its cells, or those
of the stem, as the result of the previ
ous seasons growth. 1t seems probable
that these transformations occur in the
sap after the period of its spring activ
ity begins, and in the following order
viz insoluble starch becomes soluble
gum, gum becomes uncrystallizabl'
grapc-sugar, and this, under favorable
circumstances, becomes cane-sugar
Why, then, do we find cane-sugar il
, the maple and not in the birch, an,
= why only gum as the chief ingredien
. of the sap of the vine and of those tree
which do not acquire the power O
l., active absorption until the development
of their buds? Possibly because thes
transformations require time, and tn
: maple alone is gorged with sap durin
I the six months intervening between th
fall of the leaf and the beginning c
growth in the spring. This.ailords an
I pie time for chemical changes, all
h seems to have some connection with th
fact, that the naples are the only indie
: enous trees from which crystallizab
!, cane-sugar can be profitably extract eC
:, For similar reason, since we fin
y the birches filled with sap for sewers
weeks before bud begins to expant
we may reasonably expect the form;
ton of grape-sugar at least, in then
IS and in the north of Europe q swe,
o syrup is obtained by the evaporation {
their sap. The spring sap of the vir
70 at the beginning of its motion about Il
E first of May seems to contain no sug;
, of any kind, but three weeks later
y | fax .srac N oh fac nd h
Il we NAV find a trace of grape.suga
= At this period, the beginning of veg
table growth is attended by the rap
l. exhalation of the water of the crude Sc
d and the assimilation of its gnm in Il
formation of cellulose, and this is pr
cisely the transformation which ordin
rily occurs in plants at the beginning
the vegetating season.
In regard to the circumstances whi
which affect the flow of sap from 4
sugar-maple, the following results ha
been arrived at. A careful comparis,
of the daily weight of sap from sever
trees, with the meteorological obsery
tions of the same period, conclusive
proves that while the general flow &C
responds with the season, rising to
maximum and then declining, yet {
daily and hourly flow varies with I
weather. The most unfavorable wca
er is that which is either steadily a
severely cold or uniformly warm a
foggy, while the best sap-days are su
as are bright and warm at midday,
preceded by freezing nights. Such
riations of temperature as affect
flow of maple-sap are most likely
occur when the ground is covered W
snow, because the heat of the sun c.
not then accumulate TO moderate
70 cooling influence of the night.
- most probable explanation of the eflt
of these Alterations appears to be {
the outer tissues ofthe tree are parts
emptied of their contents by the C
tracing influence of cold, the sap be
lriveninto the heart-wood the hig
parts Of The trunk \ Meanwhile, abso
tio,. s,oac IN aa ucuol uuIarnrann1