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Structure of Vegetables * 
earth has been detected by chemical analysis ; and to 
this, no doubt, their hardness and fine polish are to be 
ascribed. 
Cellular integument . — Under the epidermis, or cu- 
ticle, a succulent cellular substance is deposited ; it 
is usually of a green colour, at least in leaves and 
branches ; exists almost universally ; and has been ob- 
served in mosses and ferns. Leaves are composed al- 
most entirely of a plate of this substance, covered on 
each side by the cuticle ; and in this organ, the 
changes which are produced on the juices of plants, by 
light and air, are effected. 
The Baric .- — Next to the cellular integument lies 
the bark, which in plants or branches of one year old 
consists of a single layer, scarcely to be distinguished 
from the wood ; but in older branches, and the trunks 
of trees, the number of layers is equal to the number 
of years during which the plant has existed. The in- 
nermost layer is called liber. The bark is composed of 
numerous woody fibres, which chiefly run in a longitu- 
nal direction, and when macerated in water exhibit a 
beautiful structure resembling net-work. The Lace- 
bark tree. Daphne laghetto , a native of Jamaica, pre- 
sents a remarkable example of this structure, which has 
been already noticed in the description of that plant. 
The peculiar virtues or qualities of plants chiefly 
reside in the bark, and especially in those layers which 
are next to the wood ; it is here that the resin of the 
Fir, the astringent qualities of the Oak, and the aro- 
matic oil of the Cinnamon, are found. 
