Edgefield advertiser. [volume] (Edgefield, S.C.) 1836-current, 1840-06-18

plant Is held IN solution by water, and IN tilat
state, enters the spongiole by sort OF affinity
which, in chemical philosophy, is called capilla-
ry attraction; but from the well known fact
that the action Of this principle is confined with
in very narrow limits, the ascent of the sap from
the extremeties Of the roots; through the trunk,
TO the cXrcmetics of the branches, and into the
leaves, canno, be accounted for, but upon some
other principle less hbvious, and more difficult to
be comprchcnded. Aware ofthis difficulty ,physl-
ologis!s attempted to account for the plenolne-
non. by ascribing it to the pressure OF the at,
nlosrllcre upon the spongiolcs; thus forcing the
sap through The vessels Of The plant, upon the
same principle that column of wateris made
to ascend in Il tube by the pressure OF The at
mospherc upon the external surface OF the
water. This notion prevailed until il was ex-
plodcd by DR.. IIales; who ascer;aincd by all in
genions experiment; tllatthe sap ofthe plant as
cends with velocity sufficient 10 overcome the
| pressure of column Of wafer affect in per-
| pendicular height; which is nearly one third
greater than tho force excrted 'bv' the atnos-
pherc. That being sufficient 10 overcome the
pressure Of column of water Of only 32 fret
in perpendicular height. The opinion now
generally received is that the circulation oi'the
sap is effected by the alternate contraction and
'dIlaalion OF the sap vessels; but how this coll
traction and dataiion take place. so long rs
Vegetables are denied the functions Of sensibiliiy
and irriiahility must anprcherd, ever remain
Il profound mystery. That The san does ascend,
however and with the force ascrihcd 10 it by
Dr:flales, has been proved by ocular rdemonstra-
'ton funded on experiment; and il is pretty
well ascertained that il ascends in the infancy
Of the plant through the pith, and in its more
advanceds'atc, through the alburrlm or white
wood or in common ihrascdlogy, the sap Of
the tree, in contradistncton to The heart. The
sap. in It's ascent, undergocs little or no change,
until it reaches tic leaves ofthc plant. Here,
by means of the porosity of the leaves, il is cx-
posed to the action of the atmosphere, and is
said to have new property impaired 10 il by
tie oxygen of tic atmosphere; and thus, after
undergoing certain chemical changes and COM
binalions in Tie leaves, precisely astherenorrs
blood Of animals, by being brought in contact
with the air in the lungs becomes oxygcnatcd
and purified, the sap is fitted for giving nour-
ishment 10, and being assimilatcd with, the
propcr.snbs;ance oftl,c plaht. But the analogy
between these animal nnd vegetable functions
does not stop here; for as the venous blood of
the animal, thus purified ly being brought i'll
contact with air i'll the lungs, is by means Of
Il different sci of vessels, conduciei,back to the
heart, thence 10 be diflused through the sys-
tcm; SO the returning sap or peculiar juice Of
the plant, as il is now caIfeS- dcsccnds not in
the same vessels through which it assembled, bnt
returns through the liber or inner bark, deposit
ing in lis descent, a portion ofits nutritive pro.
pertles wherever it is most needed for the pre-
sent growth of the plant, and also laying up in
store certain portions. to be used duying the
winter and following spring, before vegetation
commences. But tile leaves have yet other i'm
portant functions 10 perform. They not only
elaborate the crude sap absorbed by the roofs,
aud prepare it for befss assimiIutcd and incor-
poratcd into the substance of the plant, hnrthcv
decompose a portion of the carbonic acid gas
of the atmosphere, and retain The carbon n.
food, whist the oxygen is disengased and
thrown of, to be employed in purifying the at
niospllcrc which has been derioraled by the
respiration of animals aud the combustion and
decomposition Of vegetable end animal SUBJ
stances. The process OF absorbing carbon and
emitting oxygen is known to take place only in
the day, or when light is present-a fact from
which psychologists conjrclured that this Glnc-
ton of the leaves is suspended during The
night; bun upon investigating the subject by
repeated experiments, lngcrhousZ and others
ascerlaincd that the process which goes on dur
ing the day, is reversed at night, oxygen being
absorbed, and catbouic acid gas being evolved
by the part
1t is obvious frcEl the analogy which ii bears
TO similar function in animals, that this pro-
cess NAV be called the respiration Of veg ge,ab!cs
Carbonaceous matter. whether il bc derived
from the soil through the medium Of the sap
vessels, Or from llie atmosphere, is The appro-
pirate food Of vegtablesi and physiSlnsis isis at
tempt TO account for the phenomena ofvcgt.n-
bic respiration, by supposing thai carbon is
generally unfit for the purposes of nutrition,
until it has been combined with oxygen in such
proportion as To form carbonic acid gas in the
plant an;. that this intricate process Of cla5ora.
ton and puriica,ion is completed by the car
bonic acid gas being dccomposed by the leaves,
during tue day, throwing OF the oxygen. and
retaining the carbon precisely in that state Of
disinlesra,ioT which fits it for being readily as
simulated and Incorporated intu the vegetable
The last function Of vegetables which time