SAP 
The bark ferves divers purpofes, for it not only tranf- 
mits the nutritious juices of the plant, but alio con- 
tains divers fat oily humours to defend the flefliy parts 
from the injuries of the weather. 
6. As animals are furnifhed with a panniculus adi- 
pofus, ufually replete with fat, which inveft and covers 
all the fiefhy parts, and fereens them from external 
cold, fo are plants encompaffed with a bark replete 
with fat juices, by the means whereof the cold is 
kept out, and in winter time the fpiculas of ice pre- 
vented from fixing and freezing the juices in their 
vefiels ; whence it is, that fome forts of trees remain 
evergreen the year round, by reafon their barks have 
more oil than can be fpent and exhaled by the fun, 
and their leaves are covered with a thick oily film 
over their furface, which prevents their perfpiring fo 
much as other plants, and alfo defends them from the 
Cold, &C. 
All the juices of barks are reducible to eight, viz. 
1. The crude, acid, watery juice, called the chyle of 
the plant. 
2. An oily juice, which, burftingthe bark in the be- 
ginning of the fummer, exfudes out of feveral plants, 
asCyprefs, Pine, Fir, Savin, Juniper, and other ever- 
greens, and fuch alone. This oil diffolves by the fmall- 
eft degree of warmth, and is eafily inflamed, and is 
that which defends the plant, which is the reafon why 
moft of thefe plants will not thrive in very hot cli- 
mates. 
F'or balm, or fatty liquor, more glutinous than oil, is 
nothing but the laft mentioned oily juice, which was 
more fluid during the fpring time, but which, by the 
greater heat of the fun, has evaporated all its molt 
lubtile parts, and is converted into a denfer liquor. 
Thus the finer part of oil of Olives being exhaled by 
the fummer’s warmth, there remains a thick balfam 
behind : thus alfo oil of turpentine, having loft its 
more liquid parts by heat, becomes of the thick con- 
fiftence of a balm. 
3. A pithy juice, which is the body of the oil itfelf, 
infpiflates, and turns black, when put into a great 
warmth : this is the moft obferved in the Pine and Fir. 
5. Refin, which is an oil fo far infpiflated, as to be- 
come friable in the cold, may be procured from any 
oil by boiling it much and long. Thus, if turpen- 
tine be fet over a gentle fire, it firft diflolves, and be- 
comes an oil, then a balfam, then pitch, and then a 
refin, in which ftate it is friable in the cold, fuflble 
by fire, withal inflammable and combuftible, difiolu- 
ble in fpirit of wine, but not in water, which makes 
the character of refin. 
Hence the oil is muft abundant in the barks in the 
winter time, the balfams in fummer, and the refin in 
*• autumn. 
6. Colophony, which is a refin ftill farther exhaufted 
of its volatile part, being pellucid, friable, and ap- 
proaching to the nature of glafs. 
7. Gum, which is an humour exfuding out of the 
bark, and, by the warmth of the fun, concofted, in- 
fpifiated, and rendered tenacious, but ftill difloluble 
in water,, and at the fame time inflammable, and 
fearce capable of being pulverized. This oily muci- 
lage ferves as a pigment to cover over, and defend 
the buds of trees from the injuries of wet and froft in 
winter, but will melt with a moift warmth, and eafily 
run from them, when the gentle warmth of the fpring 
approaches, nor is ever fo far hardened into a cruft, as 
to do any injury to the inclofed fhoot. This oilyfub- 
ftance always contains in it an acid fpirit, which is a 
prefervative againft putrefaction. 
8. A gummous refin, which is an humour fecreted in 
the bark, and dried by the heat of the fun, and thus 
conftituting a body that is partly gummous, and, as 
fuch, tenacious, foluble in water, partly refinous, and 
therefore friable, and foluble in oil, or fpirit of wine, 
but not in water. . 
Botanifts are now generally agreed, that all plants 
are furnifhed v/ith organs and parts neceflary both 
for chylification and fanguification, that they have 
veins, arteries, heart, lungs, adipofe cellules, &c. 
-SAP 
If fo, it is obvious that there muft be fome difference 
between the juices, which have not undergone the 
addon of thole parts, and fuch as have already circu- 
lated a number of times. 
The feveral juices hitherto recounted are the firft or 
nutritious juice, called alfo the chyle of the plant, un- 
der fuch alterations, and new' modifications, as it un- 
dergoes in being received, and kept fome time, in 
parts of a peculiar ftrudture, as leaves, flower, feed, 
&c. This laft juice, called the blood, is the fame nu- 
tritious juice farther altered, by being divers times 
pafied through each of thefe parts, and re-mixed, and 
at length converted into a new juice, with properties 
different from any of them all. 
To prove the circulation of the Sap, in fiances are 
brought from experiments made by Mr. Fairchild, as 
his budding and inoculating of a Paffxon-tree, whofe 
leaves are fpotted with yellow, into one of that fort of 
Paffion-tree whofe leaves are plain , for though the 
buds did not take, yet after it had been budded a 
fortnight, the yellow fpots began to Ihew themfelves 
about three feet above the inoculation, and in a little 
time after that, the yellow fpots appeared on a fhoot, 
which came out of the ground- from another part of 
the plant, which has been accounted a plain proof of 
the Sap’s circulation. 
Another inftance is, another experiment of the fame 
perfon, who grafted the evergreen Oak; or Ilex, up- 
on the common Oak. The leaves of the common 
Oak, which was the ftock, decayed, and fell off at 
the nfual feafon of the year, but the evergreen Oak, 
which was the cyon grafted upon it, held its leaves, 
and continued fnooting in the winter ; from whence it 
is concluded, that when trees drop their leaves, the 
fap keeps full in motion, and is not gone into the 
root, as fome perfons think. 
There are alfo other experiments of the fame perfon, 
which were fihewn before the Royal Society, as the 
New-England Cedar, or rather Juniper, grafted on 
the Virginian, and what is taken to prove the circu- 
lation in it, is, the branch which was grafted was left 
feveral inches below the grafting, which continued 
growing as well as the upper part above the grafting. 
And alfo another, which is the Viburnum, with the 
top planted in the ground, which was become roots, 
and the roots turned up, which were become branches ; 
which plant was in as good a ftate of growing, as it 
was in its natural ftate. 
A third experiment of his was on a Pear-tree, which 
he inarched upon two Pear ftocks in March 172 1-2, 
having the roots out of the ground, and was in a 
good fiourifhing ftate, with a branch in bloffom, 
that receives no other nourifhment but by the juices 
that return down the other two branches, which, 
though it had been done above two years, continued 
fhooting fuckers out of the root; which is efteemed 
as a proof, that the branches are as ufeful to fupport 
the roots, as the roots the branches, and thence he 
infers, that it is not ftrange that fo many trees mif- 
carry in planting, when there are no branches left to 
the head to maintain the circulation to the roots. 
A fourth experiment he made on the Cedar of Leba- 
nus, grafted on the Larix, which drops its leaves in 
the winter, yet maintained the Cedar in a fiourifhing 
condition, as if it had been on a tree which held its 
leaves all the winter, and the circulation of juices fup- 
ported the graft below the grafting, and kept it in as 
good health as above the grafting. 
In oppofition to the notion of the circulation of 
the Sap in trees like that in animal bodies, the Re- 
verend Dr. Hales, in his excellent Treatife on Vege- 
table Statics, prefents us with various experiments, 
and fays, 
When the Sap has firft pafied through that thick and 
fine ftrainer, the bark of the root, we then find it 
in greateft quantities in the moft lax part between the 
bark and wood, and that the fame through the whole 
tree. 
And if in the early fpring, the Oak, and feveral other 
trees, were to be examined near the top and bottom, 
when 
