192 Structure of Vegetables . 
when their form, structure, power Of motion, constituent 
parts, and peculiar habits, are taken into consideration. 
Of the Structure of Vegetables . 
' A plant is composed of a root, stem, leaves, flowers. 
Fruits, and seeds ; and when these different parts are 
fully developed in the progress of vegetation, the plant 
is said to be perfect ; when any of them are deficient, 
or less obvious, it is called an imperfect plant. The 
root, concealed in the earth, conveys nourishment to 
the whole plant \ the stem supports all the other parts, 
and when it is large and solid, is called the trunk, 
which is divided into the wood and the bark ; and the 
bark, forming the external covering, clothes the whole 
plant. The wood immediately under the bark is com- 
posed of concentric layers, which increase with the age 
of the tree ; and the pith, a soft spongy substance, oc- 
cupies the centre of the stem. The leaves consist of 
fibres, arranged in a kind of net-work, which proceed 
from the stem and foot-stalks by which they are attach- 
ed to the branches ; the flowers are composed of differ- 
ent parts destined to the perfection of the fruits and 
seeds ; the fruits usually consist of a pulpy substance, 
containing numerous vesicles, traversed by great num- 
bers of vessels, and seeds are constituted of a similar 
vesicular texture. Beside the parts now enumerated, 
plants contain different orders of vessels, as lymphatic 
vessels for the circulation of the sap, peculiar vessels 
which contain thick or coloured fluids, utriculi or cells, 
and tracheae or spiral vessels. 
