quickly kills and discolours them. Thus the ends of a fresh
carrot-leaf, which had been dragged into a burrow, were found after
twelve hours of a dark brown tint. Leaves of celery, turnip,
maple, elm, lime, thin leaves of ivy, and, occasionally those of
the cabbage were similarly acted on. The end of a leaf of Triticum
repens, still attached to a growing plant, had been drawn into a
burrow, and this part was dark brown and dead, whilst the rest of
the leaf was fresh and green. Several leaves of lime and elm
removed from burrows out of doors were found affected in different
degrees. The first change appears to be that the veins become of a
dull reddish-orange. The cells with chlorophyll next lose more or
less completely their green colour, and their contents finally
become brown. The parts thus affected often appeared almost black
by reflected light; but when viewed as a transparent object under
the microscope, minute specks of light were transmitted, and this
was not the case with the unaffected parts of the same leaves.
These effects, however, merely show that the secreted fluid is
highly injurious or poisonous to leaves; for nearly the same
effects were produced in from one to two days on various kinds of
young leaves, not only by artificial pancreatic fluid, prepared
with or without thymol, but quickly by a solution of thymol by
itself. On one occasion leaves of Corylus were much discoloured by
being kept for eighteen hours in pancreatic fluid, without any
thymol. With young and tender leaves immersion in human saliva
during rather warm weather, acted in the same manner as the
pancreatic fluid, but not so quickly. The leaves in all these
cases often became infiltrated with the fluid.

Large leaves from an ivy plant growing on a wall were so tough that
they could not be gnawed by worms, but after four days they were