i '
E X P L A I N E D BY THE MICROSCOPE. 21
offer fome of tliem among the variety of macerations, efpecially of fuch as have been PLATE
rubbed about often with the hands. VI I I .
A t 5. is a feition taken tranfverfely from the bottom of Fig. 2. and at 6. a view Fig. 5. 6.
of the Hke kind from the Bauhinia, Fig. 3. In the firft we fee fome remains of a
fpungy fubftance between the veffels: at 6. there fcarce is any.
C H A P . VI I I .
T H E CORONA.
I S ftrange that among all who have written on the conftrutfHoh of Trees and
Plants, the Circle which furrounds the Pith, and feparates it from the Wood,
altho' different in a high degree from both, and of a compolîtion not at all refembling
either, ihould yet have had no notice, and no name. It is indeed the moil important
part in the whole vegetable fabric ; for 'tis from this alone propagation and ehcreafe
by Branches, Buds, and Shoots, is carried on.
It has been a cuftom to fuppofe the Pith of Vegetables to be the part in which thefe
wonderful fources of increafe refide : but this theory ihrinks to nothing before a careful
enquiry. The ftate of the Pith in young Branches will be ihewn in a fucceeding part of
this Treatife ; and it will be found difcOntinucus from the original Pith of the Trunk;
and fo far from proceeding from it before the other parts, that it is in reality pofterior
to fome of them in the time of its formation. This important office of encreafe being
given to the part to which it belongs, we lhall fee that the Corona is in every
fenfe, both of conftruaion and ufe, an objedl very worthy of a careful examination.
We have hitherto been employed about parts of Plants which are perfedlly uniform
in their conftruflion. Nothing can be more JSmple than the compofition of Wood;
and if in the Blea and in the Rind there be a more elaborate ftruflure, ftill it is the
fame in all the Blea j and in the Blea of all Trees. Here we have a matter perfeûly
different ; the Corona is not uniform, but confifts of a variety of parts : nor is their
nature or their difpofition the fame in all Trees. It is not ftrange this Circle ihould fo
differ from the others; for they form and conftitute only one part of the Shoot; but
in this lie the rudiments of the whole : and the Shoot or Branch which is to contain
all thofe parts, is to receive them only from this Circle.
The Corona then is a ring, ufually more or lefs angulated in its outline, placed between
the Wood and the Pith in all Vegetables. The general Circle is cellular, compofed of
Blebs and veffels, as the Bark and Rind, and is.perfeftlyof tlieir nature; only that at
5 different