VEGETABLE STRUCTURE. 
i 7 
Pvoot, and the like, the only difference is, in the proportion of thefe con- 
flituent parts to one another, fo k*is alfo in regard to the greater difference 
of one fpecies from the refl. 
A CERTAIN number of conflituent parts, therefore, are found in all 
Vegetables, and in all the perfefl parts of every Vegetable. Thefe the 
ancient philofophy held to be only three ; the Bark, the Wood, and the 
Pith : later refearches increafed the number to five, accounting two Barks, 
the Blea, the Wood, and the Pith. To thefe, the obfervations it has been 
my fortune firfl: to make upon this fubjedl, have added two ; increafing the 
number of conftituent parts to feven : and if we add the membranes which 
inclofe thefe feveral portions, the account will run much higher. 
The two parts I have found, and which had efcaped the obfervation of 
others, are a Vafcular Series between the Blea and the Flefli of Plants 
which lall is the part analogous to the Wood in Trees; and an affortment 
of conic clurters of Veffels, taking their origin within the inner furface of 
the Flefli, and pointing inward into the Pith. 
Therefore accounting the conftituent parts of a Vegetable Body, they 
are, as we have before feen in the Hellebore Fibre, feven ; and they are 
difpofed in this order. 
1. A THIN brown outer Bark. 2. An inner Rind, green, and much 
thicker. 3. A Blea, white in colour, and many times thicker than both. 
4. A Vafcular Scries, or fingle courfe of Veffels, of a deep green, inclofed 
diftindtly between two membranes. 5. The Flefli of the Plant, of a 
yellowifli green. 6. The conic Clufters of Vefiels, of a mixed green and 
white colour. And 7. the Pith perfedly white. 
All thefe parts are feen difiindtly in the fedtions of the Fibre, the body 
of the Root, and the Flower Stalk ; fedtions of all which are given in 
Plate III. all thefe parts being portions of the entire Plant, proceeding from 
the Root to the Frudlification. In the Stalks of the Leaves we fee fewer; 
their fimple office being only to imbibe moifture from the air, and to ex- 
hale the redundance of it at other times, for the nouridiment of the Plant, 
and due motion of its Juices. Thefe are therefore to be accounted only 
as a kind of appendages to Plants ; nor are they of abfolute neceffity, for 
fome kinds live without them : to the others all the feven conftituent parts 
are necelTary, becaufe from them rife, in a plain and certain courfe, the 
Flower and Seeds. 
The Figures 25, 26, and 27, reprefent three tranfverfe fedlions, or thin 
flices, of a Fibre, as they appear before the Double Microfcope. 25 Is a 
fedlion taken from the naked upper part of the Fibre near. the body of the 
VoL. I, I Root. 
