One of the most singular instances of this is to be seen in a little
plant which is only found growing in the bogs of the Carolinas. This has
been rather cynically called the Venus Fly Trap (_Dionæa muscipula_), a
fanciful name which hides its cruel practices. Few plants have adopted a
more certain plan than the Dionæa. Every leaf which the plant produces
is the most perfect device for the securing of prey that could be
imagined.
The mechanical construction of this remarkable vegetable trap is
somewhat on the following lines. The leaf is borne at the end of a
curiously broad stalk, and is divided into two lobes; these are joined
together by a hinge-like arrangement. The outside borders of the lobes
are fringed with from a dozen to twenty long teeth. When fully expanded
the leaf lies back on the moss amid which the plant grows.
If we examine the inside surface of the lobes we shall see that these
are in the middle colored a rosy red. Just at this point will be
discovered three hairs arranged in triangular fashion.
It is interesting to consider the actual manner in which the plant
carries out its fly-catching.
As is well known, bright colors have a great attraction for insects. In
this case it is apparently the red areas on the lobes of the leaves
which possess such an attraction for insects of all kinds. Possibly they
secrete a sweet substance, but this is not definitely known. All goes on
well as long as the creatures avoid doing one thing; unhappily, this
they are almost certain to do sooner or later. Nothing happens unless
the insect brushes up against one of the hairs previously mentioned as
being on the surface of the lobes. The succeeding happenings are
disastrous for the fly.
With really astonishing rapidity the sides of the leaf snap together so
that the spines on the borders of the lobes meet. Thus, in a very brief
time a most perfect little cage is devised from which any sort of escape
is absolutely impossible. During the next half hour the sides draw in
still closer, so that the spines overlap. At this stage the leaf pours
out a copious discharge of digestive fluid, which enables the plant to
make use of the nutritious element in the fly.
[Illustration: =CRUEL PLANTS THAT ENTRAP AND KILL ANIMALS=
The light streaming through the transparent spaces induces the prisoner
to waste its strength in a vain effort to escape through them.]
[Illustration: Once below the inside edge, escape is almost impossible.
Pitchers have been found almost full of flies and other insects.]
[Illustration: Absorbed in the delights of feasting on the nectar of the
Nepenthes, the insect wanders with fatal ease down the fluted rim.]
[Illustration: The fruits of the Martynia fasten themselves to passing
animals that sometimes get the hooks caught in their mouths and die a
dreadful death.]
After an interval of several days the leaf of the Dionæa opens and
allows the hard carcass of the fly to roll away. The plant is then ready
for another meal, and unable to realize the fate which is in store for
it, another fly falls a victim. Quite often the Venus Fly Trap is able
to capture large insects.