CAROLINE.
With iron then, a cane, I suppose, will strike fire very easily?
MRS. B.
I understand that it will.—In ever-greens the epidermis is mostly resinous, and in some few plants is formed of wax. The resin, from its want of affinity for water, tends to preserve the plant from the destructive effects of violent rains, severe climates, or inclement seasons, to which this species of vegetables is peculiarly exposed.
EMILY.
Resin must preserve wood just like a varnish, as it is the essential ingredient of varnishes?
MRS. B.
Yes; and by this means it prevents likewise all unnecessary expenditure of moisture.
The parenchyma is immediately beneath the epidermis; it is that green rind which appears when you strip a branch of any tree or shrub of its external coat of bark. The parenchyma is not confined to the stem or branches, but extends over every part of the plant. It forms the green matter of the leaves, and is composed of tubes filled with a peculiar juice.
The cortical layers are immediately in contact with the wood; they abound with tannin and gallic acid, and consist of small vessels through which the sap descends after being elaborated in the leaves. The cortical layers are annually renewed, the old bark being converted into wood.