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PATTERSON v. M'CAUSLAND. 85
as has been inferred from seeing many of them grow vigorously
which were entirely hollow, then it would seem, that, on a total stop
being put to that channel of circulation, death would ensue as cer-
tainly, and almost as suddenly as by cutting the arteries of an animal.
Yet it has been observed, that early in the spring, before any thing
like a leaf has been put forth, the vine particularly, and some forest
trees, the sugar maple, &c, on a transverse incision being made
into their wood pour forth a quantity of sap, which is always seen
to proceed from the wood, and not from any layer near the bark;
which shews that the vascular tissue of the stem, by some sup-
posed to be mere dead wood, contributes largely, if not altogether,
to supplying the plant with that portion of its nutriment which it
certainly does, and must in a very great degree derive from the
earth. And it is not uncommon to see forest trees, which in the
winter or summer had been belted by a chop made all round into
the wood of the trunk, near the ground, put out their usual amount
of foliage in the following spring and sustain themselves during the
year; which proves that there is a flow of sap through the wood of
the trunk which contributes largely to the support of the vitality of
the plant. In corroboration of this, it has been also observed, that
besides the ordinary longitudinal vessels, there is what is called
the silver grain, or medullary rays, consisting of numerous thin
plates radiating from the pith to the circumference, intersecting the
concentrical layers, and visible in almost all kinds of wood; in the
oak every tube is touched by them at short distances, and slightly
diverted from its course. These plates, it is supposed, perform
some important functions in the circulation of the sap. (n)
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(n) Ruffin on Calcarious Manures, chap. 12 and 13; Rees' Cyclo, v. Circulation
of Sap and Silver Grain; Thompson's Chem. b. 4, c. 3, s. 3; Roget Anim. and Ve-
get. Physi. pt. 1, c. 1, s. 3.
'To illustrate the theory, that vegetables extract their matter chiefly from the at-
mosphere, and are of course a powerful vehicle for fixing and bestowing atmosphe-
rical manure on the earth, the following fact is circumstantially related, on account
of its complete application and to expose it to investigation. Some years ago, a lo-
cust tree at Colonel Larkin Smith's in the county of King and Queen, and state of
Virginia, received an injury which made it necessary to cut away entirely the bark
around its body for eight or ten inches, so that its bark above and below was wholly
separated, without a cortical vein between. The wound was entirely covered with
a close bandage of some other bark, which lapped beyond the edges of the wounded
bark, above and below. And the tree was left to its fate. The plaster bark never
grew to the tree, but the edges of the wounded bark, gradually approached each
other under its shelter, and after several years met and united. By the time the
wound was healed, the body of the tree above had became one-third larger than its
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