652 M i c r o s c o p i c a l E s s a y s .
C H A P . IX.
*
O n the Organization or C onstruction of T imber,
AS VIEWED BY THE MICROSCOPE.
T H E fubjeft of the following chapter opens an extenfive
field o f obfervation to the naturalift,' in which the labour o f
a life may be well employed : it is a branch, where the obferver
will find the microfcope of continual ufe, and without which he
will fcarce be able to form any juft idea of the organization o f »
trees and plants, o f the variations in the difpofition, the number,
nature, and offices o f the lèverai parts thereof.
Malphigi, Grew, Duhamel, Hill, Bonnet, and De Sauffure,
are almoftthe only writers who have treated on this fubjeft ; and
if we confider the imperfeftion o f the inftruments ufed by fome
in thofe anatomical refearches, and the little attention paid by
the reft to the advantages their favorite purfuits might have dei
rived from the ufe o f the microfcope and the di (feeling knife, we
have rather more to wonder at what has been done, than at what
remains to. be performed. One reafon that our knowledge of the
fubjeâ of this chapter is fo circumfcribed, is the general inattention
to the ftrufture of plants; to this, among' other caufes, we
may alfo aferibe the inftability and fluftuation of the different
theories on the principles o f vegetation. We are, however, fo
little acquainted with the fteps which Providence takes to lead in-
telleflual, but free agents, to the knowledge of truth, and the
various difficulties, errors, and prejudices that muft be removed
before it can fhine in it’s native colours, that it is our duty to encourage
every huibble effort towards the advancement of fcience,
that thus we may co-operate with our Creator and Redeemer in
promoting that vaft plan to which all things are now converging,
the bringing all his creatures to a ftate of truth, goodnefs, and
confequent happinefs, an end worthy o f the bell and wifeft o f
beings.*
As Dr. Hill is the firft writer who has treated this part of
natural hiftory in an orderly and fcientific manner, I (hall ufe the
names he has adopted for charaaerizing the different parts of
trees, &c. which are, 1. the rind; 2. the bark; 3. the blea;
4. the wood; 5. the corona Or circle o f propagation; 6. the
pith. Thefe are placed immediately within or under one another
; they are the effential parts upon which the ftrength of the
tree depends: in, among, and between thefe, the various veffels
are placed, which nouriffi the whole, and maintain and carry on
the vegetation of the tree, and from which it obtains it’s peculiar
qualities and virtues. Thefe veffels are of five kinds.
J uice
* See the Bifliop of Exeter’s Sermon beferd the Society for the Propagation of the
Gofpel.