the cellulose forming the cell-walls; for it is well known that all
other nutritious substances are almost completely withdrawn from
leaves, shortly before they fall off. It has, however, now been
ascertained that some forms of cellulose, though very little or not
at all attacked by the gastric secretion of the higher animals, are
acted on by that from the pancreas. {21}

The half-decayed or fresh leaves which worms intend to devour, are
dragged into the mouths of their burrows to a depth of from one to
three inches, and are then moistened with a secreted fluid. It has
been assumed that this fluid serves to hasten their decay; but a
large number of leaves were twice pulled out of the burrows of
worms and kept for many weeks in a very moist atmosphere under a
bell-glass in my study; and the parts which had been moistened by
the worms did not decay more quickly in any plain manner than the
other parts. When fresh leaves were given in the evening to worms
kept in confinement and examined early on the next morning,
therefore not many hours after they had been dragged into the
burrows, the fluid with which they were moistened, when tested with
neutral litmus paper, showed an alkaline reaction. This was
repeatedly found to be the case with celery, cabbage and turnip
leaves. Parts of the same leaves which had not been moistened by
the worms, were pounded with a few drops of distilled water, and
the juice thus extracted was not alkaline. Some leaves, however,
which had been drawn into burrows out of doors, at an unknown
antecedent period, were tried, and though still moist, they rarely
exhibited even a trace of alkaline reaction.

The fluid, with which the leaves are bathed, acts on them whilst
they are fresh or nearly fresh, in a remarkable manner; for it