i M i '
i t i v
i; ,
iii^
,2 TH E CONSTRUCTION OF TIMBER
P L A T E a filmy fubftance between them. It might feem that there are alfo tranfverre vciTds
going at fmall diftances from one of the longitudinal ones to another j but this is a
deception : a clcfe examination will iliew, that thcfc are only fpaces between part and
part of the film.
A larger power of magnifying being ufed, by changing the fixth for the fourth objeft
glafs, ilill keeping on the feventh, we ihall fee the difference between thefe empty fpaces
Fig. 2. and a vafcular ftruilure, very plainly, as at Fig. 2. d.
T o underftand rightly what the filmy part of the Rind is, we muft return to an
examination of the tranfverfe feilion, which was firft viewed. In this we lhall fee,
that the parts between veflel and veffel reprefent the mouths of open, oval cells; and,
referring this appearance to the view here given at Plate IV. Fig. r. w e llaall underftand
that each film, between fpace and fpace, is an oblong bladder j which the knife, in the
f . Fig. 4. tranfverfe feftion, has cut through. One of thefe bladders, feparate, is reprefented ztf.
Fig. 5, Fig. 4. At g. Fig. 5. are three or four, with their intermediate fpaces, and with the
longitudinal veflels continuous between them : this makes a piece of one coat of the
Rind ; and is a true and exaâ view of its compofition. In Herbaceous Plants, two
films enclofe the whole ; but it is not fo in Trees.
Fig. I.
r Fig
C H A P . IV .
OF THE Uses of the Rind.
TH E Rind, as thin as it is, and as inconfidcrable as it may feem, is a part of the
vegetable ftrudture, of the higheft and mofl: effential ufe : it covers the whole
tree, both above 5 and, what is much more important, under the ground i and contains
the great and original organs by which it grows.
T o take a right view of its importance and utility, we muft obferve fome yet unnoticed
parts of its conftruftion : and, that thefe may be rendered more diftindl than in
their ftate of nature, 'tis proper to convey coloured fluids into the feveral velTels. The
divifibility of matter has been often fpoken of with wonder, but it has never been
manifefted to the fenfes in a degree at all to be compared with what is exhibited by
fuch impregnations of vegetable parts.
I t may be now obferved, that at the letter g in Fig. 4. there appear dots upon the
highly magnified veflels: but to know what they are requires yet greater powers of the
Microfcope, and more affiftance. There are fcarce any limits to the degrees of magnifying
that may be obtained by the combination of two objeft glalTes, of different powers, as the
conftruftipn