[My experiments were tried in the following manner. Leaves were cut
off, and this does not in the least interfere with their powers; for
instance, three cut off leaves, with bits of meat placed on them, were
kept in a damp atmosphere, and after 23 hrs. closely embraced the meat
both with their tentacles and blades; and the protoplasm within their
cells was well aggregated. Three ounces of doubly distilled water was
heated in a porcelain vessel, with a delicate thermometer having a long
bulb obliquely suspended in it. The water was gradually raised to the
required temperature by a spirit-lamp moved about under the vessel; and
in all cases the leaves were continually waved for some minutes close
to the bulb. They were then placed in cold water, or in a solution of
carbonate of ammonia. In other cases they were left in the water, which
had been raised to a certain temperature, until it cooled. Again in
other cases the leaves were suddenly plunged into water of a certain
temperature, and kept there for a specified time. Considering that the
tentacles are extremely delicate, and that their coats are very thin,
it seems scarcely possible that the fluid contents of their cells
should not have been heated to within a degree or two of the
temperature of the surrounding water. Any further precautions would, I
think, have been superfluous, as the leaves from age or constitutional
causes differ slightly in their sensitiveness to heat.
It will be convenient first briefly to describe the effects of
immersion for thirty seconds in boiling water. The leaves are rendered
flaccid, with their tentacles bowed backwards, which, as we shall see
in a future chapter, is probably due to their outer surfaces retaining
their elasticity for a longer period than their inner surfaces retain
the power of contraction. The purple fluid within the cells of the
pedicels is rendered finely granular, but there is no true aggregation;
nor does this follow [page 68] when the leaves are subsequently placed
in a solution of carbonate of ammonia. But the most remarkable change
is that the glands become opaque and uniformly white; and this may be
attributed to the coagulation of their albuminous contents.