B O T 
hasbcen fixed round a tree, in fucli a’mannef that no juice 
could be traniinitted through the bark, the tree has been 
found to thicken above the ligature; but below it, to con¬ 
tinue of the fame circumference. . Hence fome have con¬ 
cluded, that the fap afcends through the bai‘k. I hole who 
are of a contrary opinion have found, that, in certain Cafes, 
the juice afcends through the bark only: for when a por¬ 
tion of the wood lifts been cut bid, and the bark exactly 
replaced, the growth of ti,ie tree has been found to Lq- on 
unchanged : hehce, it i's 1 laid, tiiat the juice isTrafiimitted 
equally through all pa tits 'of vegetables. Tile experiments • 
adduced oii each fide df the quefilon are juft,'but the rea- 
foningson thefe, by each party, feent equally inconclulive. ' 
The analogy of animal nature appears to favour the opi¬ 
nion, that the juice rifes.through the-wood only, and de- 
feends only through the. bark; but this analogy is not 
complete throughout. The arteries.are not placed in the 
internal parts alone, nor the veins in the external, but they 
accompany each other through every part of their ditlri- 
bution. In vegetables, the fap riles/wr/rnhe: roots, but 
the proper juice defeends towards them ; in the defeent of 
the juice, the wood acquires its growth, and abforption is. 
a conftant aiSlion of the leaves. Thefe oble.rvations render 
it probable, that there is a circulation of the juices;; and, • 
if there be, the veilels which perform it, we may'reafon- 
ably believe, accompany each other through every part of 
their courfe. 
Of thf, LWNfEAN, or SEXUAL SYSTEM. 
. A perfect plant is compofed of a root; of a trunk or 
(lem, with its branches; and of leaves, flowers, and fruit. 
By fruit, both in herbs and trees, is meant perfcB feeds, 
whether accompanied, or not, with an eatable,part. The 
fruBification, which implies : the flower and the fruit, re¬ 
quires the mod minute invefligation ; for on this the fexual 
fyflem is principally founded. Therefore, to explain tiiis 
fyftem, and illuftrate the curious fabric of a vegetable, we 
lliall inveftigate its parts, and trace it upwards from the 
root to the flower; and then unfold the characters of the 
twenty-four dalles, into which Linnaeus has divided the 
whole vegetable kingdom. 
Of the ROOT, 
The radix, or root, imbibes the nutritious juices of the 
earth, and tranfmits them to the other parts. In point of. 
duration, they are divided into three dalles, viz. annual, 
or abiding only one year ; biennial, abiding two years; and 
perennial, abiding and regerminating feveral or many years. 
Every root, after it lias arrived at a certain age, acquires 
a double (kin. The firft is coeval with the other parts, 
and exifls in the feed ; but afterwards there is a ring fent 
off from the bark, and forms a fecond ikin ; as for exam¬ 
ple, in the root of dandelion, towards the end of May, the 
original or outer (kin appears fhriveiled, and is ealily fe- 
pqrated from the new one, which is frelher, and adheres 
more firmly .to the bark. Perennial plants arc fupplied in 
this manner with a new Ikin every year; the outer one al¬ 
ways, falls off in the autumn and winter, and a new one is 
formed front the bark in the iueceeding fpving. The ikin 
lias numerous cells or velfels, and is a continuation of the 
parenchymatous part of the radicle. However, it does 
not confift folely of parenchyma; for the mievofeope thews 
that there are many tubular ligneous veffels interfperfed 
through, it. 
When the (kin of the root is removed, the true cortical 
fubfrance or bark appears, which is alfo a continuation of 
the parenchymatous part of the radicle, but greatly aug¬ 
mented, The bark is of very different fixes. In mo ft trees 
it is exceedingly thin in proportion to the wood and pith. 
On the other hand, in carrots, it is almoft one-half of the 
femidiameter of the root; and, in dandelion, it is nearly 
twice as thick as the woody part. The bark is compofed 
of two fubtfances; the parenchyma, or pulp, which is the 
principal part, and a few woody fibres. The parenchyma 
is exceedingly porous, and has a great refentblance to a 
Vo J,. III. No. 127. 
A NY. 237 
fponge; for it fiirivels confiderably when dried, and dilates 
to its former dimentions when infilled in water. Thefe 
pores or vctfels arc not pervious, Ifo as to communicate 
with each other ; but confift of diftifuT cells or bladders, 
fCarccly vitible without the alliftance of the microfcope. 
In all roots, thefe cells are Conftantly filled with a thin 
watery, liquor. They arc generally of a fplierical figure ; 
though in forrie roots, as the buglofs and dandelion," they 
are oblong. I11 many roots,' aS the horfe-radifh, piony, 
afparagiis, potatoe, &c. the parenchyma is of one uniform 
ftj'rtcH me. But in others it is more divertified, and puts 
on the fliape of rays, running from the centre towards the 
circumference of the bark. Thefe rays fometimes run 
quite through the bark, as in lovage; and fometimes ad¬ 
vance towards the middle of it, as in melilot, and moft of 
the leguminous and umbelliferous plants. Thefe rays ge¬ 
nerally’ftand at an equal diftance from each other in the 
fame plant; but the’diftance varies greatly in different 
plants. Neither are they of equal file's: in carrot they are 
exceedingly filial 1, and fcarcely difcernible ; in melilot and 
chervil, they'are thicker. They are likewife more nume¬ 
rous in forwe plants than in others. Sometimes they are 
of the fame thicknefs from one edge of the bark to the 
other;- and fome grow wider as they approach towards the 
Ikin. The velfels, with which thefe rays are amply fur- 
niftied, are fuppofed to be air-y.eftels, becaufe they are 
a Ivy ay si found to be dry, and not fo tranfparent as the vef¬ 
fels which evidently contain the fap. 
In all roots there are ligneous veffels difperfed in dif¬ 
ferent proportions through the parenchyma of the bark. 
Thefe ligneous veffels run,longitudinally through the bark 
in the form of final! threads, which are tubular, as is evi¬ 
dent from the fifing of the fap in them when a root is cut 
tranfverfely. Thefe ligneous fap-veffels do not run in di¬ 
rect lines through the bark, but at fmall diftances incline 
towards one another, in Inch a manner that they appear to 
the naked eye to be inofcttlafed ; but the microfcope dif- 
covers them to be only contiguous, and braced together 
by the parenchyma. Thefe braces or coarffations are very 
various botli in fize and number in different roots; but in 
all plants they are moft numerous towards the inner edge 
of the baik. Neither are thefe veilels tingle tubes ; but, 
like the nerves in animals, are bundles of twenty or thirty 
fmall contiguous cylindrical tubes, which uniformly run 
from the extremity of the root, without fending off any 
branches, or differing any change in their fize or (iiape. 
In fome roots, as parfnep, efpecially in the ring next the 
inner extremity of the bark, thefe velfels contain a kind 
of lymph, which is fweeter than the lap contained in the 
bladders of the parenchyma. From this circumflance they 
have got the name of lymph-duBs. Thefe lymph-dudts 
fometimes yield a mucilaginous lymph, as in the comfrey; 
and fometimes a white milky glutinous lymph, as in the 
angelica, fonchus, burdock, icorzonera, dandelion, &c. 
The lymph-dtnTs are fuppofed to be the veffels from which 
the gums and balfams are fecerned. The lymph of fennel, 
when expofed to the air, turns into a clear tranfparent bal- 
fiam ; and that of the fcorzonera, dandelion, &c. condenfes 
into a gum. The fituation of thefe velfels is various. In 
fome plants they (land in a ring or circle at the inner edge 
of the bark, as in afparagus; in others, they appear in 
lines or rays, as in borage ; in the parfnep, and feveral 
other plants, they are moft confpicuous towards the outer 
edge of the bark ; arid in the dandelion, they are difpofed 
in the form of concentric circles. 
The wood of roots is that part which appears after the 
bark is taken off, and is firmer and let’s porous titan the 
bark or pith. It confifts of two diftindl liibftances, viz. 
the pulpy or parenchymatous, and the ligneous. The wood 
is conneiSfed to the baik by large portions of the bark in¬ 
fected into it. Thefe infertions are mo/ily in the form of 
rays, tending to the centre of the pith, which are eatily 
difcernible by the eye in a tranfverfe lection of moft roots. 
Thefe infertions, like the bark, confift of many veilels, 
moftly of a round or oval figure. The ligneous veilels are 
3 P generally 
