I. [ J i m
' - i ' i j
E X P L A I N E D BY THE MICROSCOPE. 49
If this conflruiftlon of the Wood, which is fo eafily underftood ia the prefent inftance,
be always held in mind, as we examine olhers, the fccrets of the compofition
will be laid open to us with Icfs pain.
11. O f T h e L e n g t h o p t h e C o k e s
IN THE A c a c i a Decidua.
A Tree which affords an inftance of equal fimplicity with the Dog-Wood.but in a PLATE
new form, is the Acacia Decidua: a feilion of which is given at Plate XXV. yet the
fmallnefs, or, if it may be better underftood, the delicacy of its parts, renders it Icfs
obvious 5 and leads us, as by a fingle ftep, from that fimple kind to the appearance
of the more complex. The Rind in this Acacia is very thin} the Bark is alfo thin j
a b: and in the Blea, which holds fome breadth at c, are difpofed VelTels fo very a b c
much refembling the interiora of other Trees, that we ihould fuppofe them of the
fame nature, if we did not firft fee them in a place where the intima alone can ftand;
and if the firmnefs of the matter with which tliey are filled did not confirm i t : but,
beyond all, their own ftrudure 5 for they are funple VelTels > their fides are not vafcular.
The Wood, which lies nearly within thefe,. confifts of very long and narrow cones.
The parietes of thefe are extremely diftinft, tho' fine; and the whole Wood is pierced
with Sap-Veflels fo large, that its own vafcular ftrudture, which is indeed in all Wood
very delicate, gives the idea of a compaft and folid fubftance. Nature, in this inftance,
giving all to the Wood, .contra<fls the Pith, and half annihilates the Corona: 'tis
very lingular : but ftill the parts of that circle are to be feen in thefe young Shoots of •
the Acacia Decidua: and in thofe of more ftanding they become as large as ufual.
Why and to what end Nature, where nothing is done in vain, gives this exuberance
of Wood to this, and the fcanty ftore of it to Dog-Wood, are queilions for a very high
philofophy.
III. O f t h e t h i c k Parietes
OF THE R o b i n i a Caragna.
IMi:
i
He who will join with me to purfue the laft named plan and try if it tnay be found PLAT E
Vhy, in the Robinia now before us, the fides of thofe cafes wherein the Wood is held XXVI.
are remarkably thick, or, if we may ufe fo ftrangc a word, fo coarfe; will perhaps
open the way to a knowledge of the nature o f Trees j which, tho' propofed more than
two thoufand years ago by Theophraftus, has pafled thro' the hands of all his fucceffors
untouched, fo far as their writings have informed us j therefore, at leaft, not happily
followed.
The appearance of a feftion of this Tree is given in Plate XXVI. In the Rind and
Bark, « nothing is particular. The Blea is very firm, compafb, and delicate. In the a b
Wood there are, as it were, fliadows of circles j nothing real: but ftill we find the Sap-
7 VelTels