rendered oppressive by the state in which he finds himself. Now it may
be easily proved, that a similar instinct to that which induced the
unfortunate sufferers in the black-hole of Calcutta to struggle with the
last efforts to approach the solitary aperture which admitted air to
their dungeon, and to throw from them their garments, in order to
encourage the exertions which nature made to relieve herself by
perspiration, is proper, also, to the noblest of the vegetable tribe.
Look at a wood or plantation which has not been duly thinned:--the trees
which exist will be seen drawn up to poles, with narrow and scanty tops,
endeavouring to make their way towards such openings to the sky as might
permit the access of light and air. If entirely precluded by the boughs
which have closed over them, the weaker plants will be found strangely
distorted by attempts to get out at a side of the plantation; and
finally, if overpowered in these attempts by the obstacles opposed to
them, they inevitably perish. As men throw aside their garments,
influenced by a close situation, trees placed in similar circumstances,
exhibit a bark thin and beautifully green and succulent, entirely
divested of that thick, coarse, protecting substance which covers the
sap-vessels in an exposed position.

There is a singular and beautiful process of action and re-action which
takes place betwixt the progress of the roots and of the branches. The
latter must, by their vigour and numbers, stretch out under ground
before the branches can develope themselves in the air; and, on the
other hand, it is necessary that the branches so develope themselves, to
give employment to the roots in collecting food. There is a system of
close commerce between them; if either fail in discharging their part,
the other must suffer in proportion. The increase of the branches,
therefore, in exposed trees is and must be in proportion with that of
the roots, and _vice versâ_; and as the exposed tree spreads its