affected in a peculiar manner by the secretion poured out of their
mouths. The upper surfaces of the leaves, over which the worms had
crawled, as was shown by the dirt left on them, were marked in
sinuous lines, by either a continuous or broken chain of whitish
and often star-shaped dots, about 2 mm. in diameter. The
appearance thus presented was curiously like that of a leaf, into
which the larva of some minute insect had burrowed. But my son
Francis, after making and examining sections, could nowhere find
that the cell-walls had been broken down or that the epidermis had
been penetrated. When the section passed through the whitish dots,
the grains of chlorophyll were seen to be more or less discoloured,
and some of the palisade and mesophyll cells contained nothing but
broken down granular matter. These effects must be attributed to
the transudation of the secretion through the epidermis into the
cells.

The secretion with which worms moisten leaves likewise acts on the
starch-granules within the cells. My son examined some leaves of
the ash and many of the lime, which had fallen off the trees and
had been partly dragged into worm-burrows. It is known that with
fallen leaves the starch-grains are preserved in the guard-cells of
the stomata. Now in several cases the starch had partially or
wholly disappeared from these cells, in the parts which had been
moistened by the secretion; while it was still well preserved in
the other parts of the same leaves. Sometimes the starch was
dissolved out of only one of the two guard-cells. The nucleus in
one case had disappeared, together with the starch-granules. The
mere burying of lime-leaves in damp earth for nine days did not
cause the destruction of the starch-granules. On the other hand,
the immersion of fresh lime and cherry leaves for eighteen hours in