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P L A T E
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F i g . 2.
F ' g - 3-
F^g- 4-
T H E C O N S T R U C T I O N O F TIMBER
I t cannot but be obfcrved, even by the leail curious, that the outline o f thefe vefTels
is coropofed of a Ring of oval apertures, />.• thefe are in reality the mouths of other
v c f l e l s ; and the refult o f the obfervation is, that the very coats o f thefe veflels are themfelves
vafcular. A view o f an arrangement of thefe veflels, as they appear in a tranfverfe
Slice cut from one o f the Vafa propria of this Pine, is given at Fig. 2. Thefe veifcls
appear, by the ftrifleft enquiry I have been able to make, to be of the fame nature with
thofe which conAitute the Packets in the Vafa propria exteriora; fo that if we conceive
one of thofe Packets opened in its centcr, and the veflels driven every way outward till
they are flopped by the fubftance o f the Bark, they wi l l give us an idea o f the ftrufture of
the Vas interior, which is no more than a great cyl indri c hollow formed in the center of
f u c h a Packet. A view of fuch a velTel, as taken out of the Pine, is given at Fig. 3.
and at Fig. 4. is reprefeiued their exa£l difpofition in a fomewhat older Branch, where
the hardening of the parts has driven them clofe together, and where they appear as in
the hol low o f fuch a piece; the W o o d Blea, and even part o f the Bark, being pulled away.
F e w Trees aftbrd more beautiful objeds than a piece like this, of the Pine, before the
Microfcope here defcribed, ufed in the oblique manner.
F r om what we have feen of the conf truf t ion and ufe of the Vafa exteriora, the nature
o f the purpofes thefe anfwer in the Vegetable Oeconomy is not hard to trace. If, as is
moil probable, the veflels o f the coats of thefe, are the fame with thofe, they are filled
w i t h the eflential jui c e s of the R ind; and from thofe cells 'tis probabl e that they difcharge
the matter they contain into thefe great receptacles, thro' apertures in that part of their
furface which forms the infide o f thefe velTels: but this is no more than opinion.
C o n j e d u r e muil be carefully diftinguiflied from obfervation j and it muit be owned it
may err here : for thefe veflels are fmall, and fo difficult to be got at, that I have never
been able to fee cither thefe openings, or their contents. But whether it be by thefe or
b y any other means the Vafa interiora are fupplied, their office is certain j they hold .
the rich juice, fecreted from the nourifhmeiU of the Plant, perfedly feparate from all
the other fluids : and from their fituatioa in the oater Bark, it is evident whence it
happens that in this part we find the virtues and the flavours of Vegetables mof l I'efide.
E X P L A I N E D BY T H E MICROSCOPE.
C H A P . nr .
BR THE V A S A PROPKIA INTIM/
X T O T W I T H S T A N D I N G the r e are in the conftruffion of a piece tf F L A T E
T i m b e r two arrangements of Veflels wi thi n thefe Int ima, the great Sap Vef fel s XIIl.
b f the Wo od, and thofe of the Corona; yet as the former are not of the nature of
Ihc Vafa propria, (not carrying any peculiar j uices, but only Sap, which is nearly the
fame in all Trees) and as the others are not of one kind, but a mixture of feveral.
and indeed are only repetitions in miniature of thefe. and the preceding; the Reader
w i l l not difpute the name Intima to the prefent.
T h e y are large, confpicuous, and very important veffels : their natural place is in
the Blea ; the part of a Tree which lies between the Bark and the W o o d : they are
never feen in any place exterior to this, but fomctimcs they are repeated in the very
f u b l i a n c e o f the Wood ; nay, and in the Corona itfdf ; in forae degree difplacing and
intercepting the other parts.
I t is very effential to fee thefe in a Tree where tliey are mof t confpicuous ; for their
b e i n g thus intermingled among other parts renders them in many inftances obfcure:
a t l e a f t the bed obferver will be able to find them much the more readily in other
kinds, from having once feen them where they are thus obvious. Their coats are
t h i c k e r than thofe o f any other veffels; but in fome kinds they have alfo a colour in
their contents that renders all doubt concerning them impoffible.
T h e Tree in which they appear mod palpable of all, is the Kfcidi a Erythrina. In
thefe they have a fcarlet colour, never to be overlooked : and it happens that the
other parts lie fo confpicuous and fo regularly about them, that they mud be known
every where, for ever, by any one who has once feen them here. A view of a
tranverfe feclion, from the Shoot of this Tree, is given at Plate XIII. Fi». : I„ Fig ,
this the Vaf a propria interiora {„) hold a diftinguiflied place ; and juf t within their ' /
c i r c l e he the intima ; large, (ingle, confpicuous, (fee the letter i ) difpofed in a man- i
ner perfeffly fingular ; certain affemblages of them, about three in number, following
their exaii courfe in the Blea, but alternately arranged in lines and triangles. Beiides
theft there appears here and there one of them loofe and unarranged among the
Sap Veffels of the Wood, as at c. And in the Corona there appears at d a perfeS r d
c i r c l e of them, in the fame alternate arrangement of lines and triangles.
I Th e
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