E X P L A I N E D EY THE MICROSCOPE.
C H A P . iV .
P A R T I C U L A R I T I E S T H E CORONAL VESSELS
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T H E I R D ISTINCT APPEARANCE
I N THE SUMACH.
IT has been ihewn that the Vef lelsof the Corona are no other than the feveral Veflel s P L A T É
o f the former kinds, only that they are here in a fmaller compafs, and of lefs fize.
T h e y need not be defcribed particularly after thofej for greater and lefs is no diftinñion
in phi lofophy: nor have thefe any other. Yet, as there is in Sumach an opportunity laid
before the curious eye of being certified of this truth, it may be ufeful, as well as agreeable,
to (hew it. A fe£tion of this Tree is given, Plate X L I I . where the firft fight will
i h ew how much it approaches t6 the herbaceous tribes in the glandular conftruñion of
its Rind, and in its vafl: Pith. Happily in this Tree the Corona makes a more diñinít
c i r c l e , more defined in itfelf, and more feparate in its parts, than is to be feen elfewhere.
W h e n we have fol lowed the conf t ruf l ion of this Shoot from without, and feen its brown
and hairy Rindj fl, lined by the dark green juicy Bark, and withi n this the paler, y e t á h
green Blea, c, we diftinguiih very finely the ellipfes of Wood, d a n d within thefe the c d
Corona. Its white circle, e, has let loofe, as it were, the clufters,/"} and one o f thefe, e f
feparated, waQied clean, and viewed by a greater power of glafles, appears as at Fig. 2. Fig. 2.
where the Rind andBark, thrown to the ends, I. z. ihew dots at 3. whi c h arehere the i. 2. 3
embryo Vafa exteriora; and larger fpecks at 4. the interiora. At 5. in that whi c h is to b e 4 j.
the Blea, are dots, tho' fmall, yet particular in colour ; and 'tis impoíTiblCj both from
that and from their place, to doubt their being Vafa intima in miniature. And in the
central part, at 6. are Sap'Vef lel s , whof e openings, as is the cafe in mof t other inftances, 6.
are fo big as almoft to look prepofterous. The Vafa exteriora, in the entire feétion,
cannot but be admired; they are firm, full of a mi lky juice, and when the feáiion, if
o f any thicknefs, has lain but a few minutes, they rife from its furface, being too "
folid to ihrink with the reft. In the Pith, at a fmall diftance, within the clufters of
the Corona, g, are to be feen, very beautifully, purple Veflels, h, whofe form and g b
ftrudure fliew them Vafa intima.
III
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• • ' I I I
C H A P . V.
OF THE DISTRIBUTION OF THE SAP-VESSELS, PARTICULARLY IN THE OAKS.
TO form a proper judgment of thefe Veflels, too much mifunderftood by many, PLATE
w e can no where follow them better than in th.c Oak j the firmeft, ftrongeft, XLIII.
heavieft o f T r e e s ; yet pierced beyond all others by thefe VeiTels. The y have been ihewnin
their natural ftate in Plate III. in the common Engliili O a k : and that fize and diftribution
o f them, however ftrange it might feem to an unaccuftomed eye, is not peculiar to that
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