E X P L A I N E D BY THE MICROSCOPE.
C H A P . V.
OF THE Ve s s e l s of t h e Coroka.
" i ^ E have ften what arc the diiftrcnces of Veffds ¡n the Vegetable Strufture; for PLATE
» ' we have already viewed all their kinds. The Corona is the whole in minia- XV.
ture : it contains the embryo's of future Shoots ; and therefore muft contain their
VeiTels, and can contain no other.
We have feen, that of the two parts whereof the Corona confifts, the Ring, and the
Clnfters, the Ring is the fame with the B.ir!i ; it therefore has the fame Veflcls. Their
appearance indeed is only that of the fame objeils viewed with a lefs power : only in one
point there is a roanifeft diftinflion. This is in thofe openings which a great magnifying
power difcovers in thefe VeiTels. Thefe are proportionally twice as big in the Bark VelTds
of the Corona, as in thofe of the grown Branches : nor is it difficult, from what has been
faid of their ufe, to guefs the reafon. Thefe Veffels are reprefented at Plate XV. Fig. i. F],.
As the VeiTels of the Circle or Ring of the Corona differ in nothing elTential from
thofe of the Bark J neither do the VeiTels of the Cluliers differ more from thofe of the
feveral parts of the grown Tree, of which they are the embryo's. It is often poffiUe
(I cannot indeed fay it is always eafy) to diffinguitti the Vafa intima in the outer and
inner ends of each duller ; among the VeiTels of the Blea. Thefe, as well as the
Blea VeiTels, are very difficultly viewed with any diftindlnefs in this compail and
crowded condition I wherein they Hand in the duller : but what difference I have
been able to fee, in thefe leffer Blea VeiTels, is, that they have fewer but larger mouths
than in the Blea of grown Shoots j and that there is an utter want of the fpungy interftitial
matter which in that Hate keeps them feparate and at a diffance : and that the
Vafa intima, the proper objed of enquiry here, have thinner coats, and are not fo
perfeitly cylindric.
In the central part of every Clufter we are to expea to find thofe vali Sap VilTels
which feed the whole interior part of the Tree ; nor are we difappointed : they are
indeed yet larger in proportion here than we find them In the grown Branches ; for
•tis here they have their greateft ufe : 'tis thefe alone that can ftipply the Shoot in its
firft puQiing out from the Branch, It is to grow before it has coninmnication with
the outer air; and 'tis by thefe Veffels, which here are always full, tho' in other parts
they are fo only at particular feafons, that the growth of an angle of the Corona is to
be fupported and fupplied in its egrefs into a Branch. ^
K B O O K
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