E X P L A I N E D B Y T H E MICROSCOPE. 43
W i t h what pJeafiire will the curious eye, having once acquainted itfclf wi t h all thefe PLATE
parts in their diftin£t and infant ftate, purfue them in other inftances, where, in their
adult condition, they have united themfelves for ftrength one wi th another, and often loft
even the appearance of their original conftruition !
, The Pith in the Dog-Rof e is alfo a very beautiful objeift. It has, in a flice of this
-. thicknefs, the appcarance of ftarry forms, with oval rays : but this illufioii vaniflies on
cutting a thinner flice. When one is viewed of a thoufandth part of an inch, they appear
only fimple Blebsi
I
k
. r
C H A P. It,
loF D i f f e r e n c e s in t h e Ba r k i
'1:
^ " T ^ H E Rind of Trees^ being no more than an out-caft of the Bark, is of little ¡PLATE
importance to them J and we find in it very little variation : but in relpeil of XIX.
the Bark it is much other wi fe. This is a very effential part in the Tree j its growth
depending, in a great meafure, upon it j and its qualities: and we find it accordingly
very different} in fubilance, quantity, and nature, in various kinds.
I t is originally the outer membrane, covering the Lobes of the Seed : even there it
may be feen, juft as in the Branch of a Tree, in form of a kind of fpunge; compofed
o f flatted bladders : and in the fucceeding g rowth, the outer ranges of thefe bladders,
drying, become what we call the Rind j for that part has no exiftence in the feed ftate:
i t is formed by the operation of the air j it is ftretched by the fwelling of the Wood}
i t is caft off once in a feafon, as fnakes caft their ikins: but not entire, only in frag,
ments. Mean time the Bark remains what it was, covering the rnore ¿ibftantial
parts, the Blea, the Wood, and the reft, and feeding them by a continual fupply of
nouriihment from its fpungy fubftance, always fupplied with water: this it draws
up frefh as faft as it is drained off, and continually feeds every fubjacent part. It
protefts all from external injuries alfo, and defends them from the effeds of cold.
For thefe purpofes it is variouily difpofed in different Trees. In the hardy and dow
growing, as the Oak and Chefnut, it is thin: in the quick growing, as Wi l low, Pop- r
lar, and the like, it is thick : and, what is more worthy yet of regard, is, that altho'
i t is laid fmoothly and in an even line over the Blea in moft Trees, yet in fome its
inner verge is radiated^
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M There
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