S A P 
and thus increafes by apportion* ' aiid hence it may 
be, that hollow, carious, or rotten trees, which have 
neither pith nor wood, excepting juft enough to fuf- 
tain the bark, grow and bear. 
Some contend for the wood, which they obferve to 
confift of fiender capillary tubes running parallel to 
each other from the root up the trunk, being proper 
to receive in a fine vapour in the afcent whereof 
the fibres become open, and their fubftance increafed, 
and thus the trunks of trees are faid to increafe in their 
circumference. 
As for the pith ; as the w r oody fubftance of the trunk 
becomes more woody, the pith is comprefied and 
ftresghtened to fuch a degree, that in fome trees it 
quite difappears, whence it feems, that its office in 
vegetation is not very important, fince its ufe is not 
perpetual. By its fpongious fubftance it fhould feem 
fitted to receive any fuperfluous moifture tranfuding 
through the pores of the woody fibres ; and, if by the 
excefs of fuch moifture, or the like caufe, it corrupt 
and rot, as it frequently happens in Elms, the tree 
feems not to grow worfe for it, which is a convincing 
proof it is of no great ufe. 
The learned Dr. Boerhaave diftributes the juices of 
plants into fix clafles : 
1. The firft clafs comprehends the crude nutritious 
juice, or the juices of the root and Item of plants, 
which are little more than the mere matter of the ele- 
ment, as drawn by the root from the body it adheres 
to, whether it be earth, water, or the like. 
This juice is found in every part of the plant, and 
therefore may be held an univerfal juice •, yet he con- 
siders it as the juice of the root and ftem, becaufe it is 
chiefly found in them. 
This he takes to be the fubacid watery lymph with- 
out any fpecific tafte or fmell, as not being yet ar- 
rived to the, maturity of oilinefs. 
To this clafs belong thofe juices, which diftil in great 
abundance from wounds or incifions made in the 
woody parts of plants ; fuch, e. g. is that tart liquor 
oufing from the root of the Walnut-tree, when cut off 
in the month of May. 
Such alfo is that limpid fubacid humour flowing out 
very plentifully at an incifion in the Birch-tree, in the 
month of March, to the quantity of feveral gallons in 
a few days. 
Such alio is the juice iffuing out of the Vine wounded 
in the fpring time, which always taftes tardfh, and 
ferments like the Grapes themfelves. 
This juice may be efteemed as yet foffil, being gene- 
rated of and in the earth ; for the juice of the earth, 
being received into the canalsof thefe plants retains its 
nature during two or three circulations, nor doth it 
immediately commence a vegetable juice. 
This clafs of juices therefore he accounts as the chyle 
of the plant, being chiefly found in the firft order 
of vefiels, viz. in the roots and the body of the plant, 
which aniwer to the ftomach and inteftines of animals. 
2. The fecond clafs of the juices is that of the leaves, 
which are the real lungs of plants, and accordingly 
make a further change of the juice, which they re- 
ceive from the roots and ftem by force of the air. 
The juice of leaves is different therefore from the 
firft juice, as being more fulphureous, and farther 
elaborated •, not that it derives any fulphur from the 
fun, but that, its watery part exhaling, it becomes 
more oily, and lels volatile. 
•The juice of leaves he diftinguifln.es into three kinds : 
The firft is the nutritious juice of the leaves, which 
is that already defcribed, only further elaborated in 
the minute veficulte of the leaves, and confequently 
lefs watery, and more oily and faccharine. 
The fecond is wax, which, exfuding out of the leaves, 
adheres to the lurface, and is fcraped off by bees with 
their rough thighs to build their combs withal. This 
is chiefly afforded by Lavender and Rofemary, upon 
the latter of which the wax may be plainly perceived 
fticking to the leaves of it. 
The third is manna, not that with which the Ifraelites 
were fed in the defer t, but a drug fold among us j it 
is an eflentiai faccharine fait exfuding chiefly by nigfity 
•and in the fummer feafon, from the leaves of a fort of 
Afh growing in Calabria and Sicily, and adhering 
thereto in the form of a cruft, to be gathered the next 
morning ere the fun is up. 
The like fubftance is found to exfude from the leaves 
of the Linden-tree and Poplar, in the heats of May 
and June, at which time they have an honey tafte, 
and are even feen with a fatty juice on them, which, 
at the approach of the cold evening, gathers into 
grains. 
3. The third clafs of juices are tltofe of flowers, or 
the genital parts of plants : in thefe are, 
Firft, a pure elaborated volatile oil or fpirit, wherein 
the particular fmell of the plant or flower refides, and 
which, by reafon of its extreme volatility, exhales 
fpontaneoufly, infomudi that if the flower be laid for 
fome time in a warm place, the odorous juice or fpirit 
will be all fled. 
The fecond is the juice expreffed from the flower, 
which in reality is the fame with that of the root and 
leaves, only farther prepared •, it is thicker than the 
former, and has fcarce any fmell at all. Thus, if you 
bruife a Hyacinth, or other fragrant flower, and ex- 
prefs the juice, it will be found altogether inodorous^ 
The third is the fweet juice called honey, which ex~ 
fudes from all flowers, Aloes, Colocynthus, and other 
bitter flowers not excepted. 
In all male flowers that have utricles at the bottom of 
the petala, which Dr. Linnseus ftyles the neftarium, 
is found a viicid, ruddy , fweet juice in fome plenty, 
and accordingly we fee the children gather .Cowilips, 
Dead Nettle, Honey fuckles, &c. and fuck the honey 
from them. The bees too vifit thefe flowers, and 
putting in their probofcides or trunks, fuck out the 
honey, and load their ftomachs therewith to be after- 
ward difcharged and laid up in their combs, fo that 
honey is a vegetable juice. 
4. The fourth clafs of juices are thofe of the fruit and 
feed, the preparative whereof is nature’s final work, 
which performed, the plants feem to die for a time, as 
all animals are feen to languifh after the emiffion of 
their femen. 
The juice of the fruit is like that of the root, only 
farther elaborated. 
The juice of the feed is an eflentiai oil or balm elabo- 
rated and exalted to its laft perfection. This juice or 
oil is not found in the very point or embryo in the 
center of the placenta ; all we meet with in that part 
is a few fine watery particles fecreted from the placen- 
ta, but it is in the placentuli or cotyledons them- 
felves, which confift of innumerable little folliculi or 
cells, wherein this juice is contained, ferving to de- 
fend the embryo, and preferve it from being cor- 
rupted by water, which, it is well known, will hardly 
pals through oil. 
Thus, if you take, e. g. Fennel-feed, cut it through 
the middle, and apply it to the microfcope, you will 
eafily perceive a clear (hining oil in the cells of each 
lobe invefting the tender embryo. Without this oil it 
were impofllble a feed fhould five a month, and much 
lefs a year or two entire and uncorrupted in the 
ground. 
This oil is found in the feeds of all plants ; in fome,* 
e. gr. in Almonds, Cocoa-nuts, &c. in very great 
quanties ; in others lefs, as Pepper, Arum, &c. where 
one would fcarce imagine any oil at all •, and thefe 
feeds loofe their vegetative quality very foon. 
5. The fifth clafs of juices are thofe of the bark, which 
is an artful congeries or bundle of perfpirative du6ls* 
and abforbent vefiels. 
Of thefe juices there are divers fpecies, for the feve- 
ral humours raifed and diftributed through the leaves* 
flowers, and other parts of the plants, have all circu- 
lated through the bark, and according^ are frequent- 
ly found to diftil from wounds made therein. In fome 
cafes, even the whole plant is no more than bark, the 
pulp having been eaten out, as in Willows, Elms* 
&c. which live a long time in that ftate,- 
The 
I 
