The variety of the pitcher plant (_Sarracenia variolaris_) found in
North America is carnivorous, being a feeder on various animal
substances.
Mrs. Mary Treat, an American naturalist, made, a few years ago,
several experiments upon the plants of this species to be found in
Florida; and to the labors of this lady the writer has been indebted,
in some measure, in the preparation of this paper.
The _Sarracenia_ derives its name of "pitcher plant" from the fact of
its possessing the following curious characteristics: The median nerve
is prolonged beyond the leaves in the manner of a tendril, and
terminates in a species of cup or urn. This cup is ordinarily three or
four inches in depth, and one to one and a half inches in width. The
orifice of the cup is covered with a lid, which opens and shuts at
certain periods. At sunrise the cup is found filled with sweet, limpid
water, at which time the lid is down. In the course of the day the lid
opens, when nearly half the water is evaporated; but during the night
this loss is made up, and the next morning the cup is again quite
full, and the lid is shut.
About the middle of March the plants put forth their leaves, which are
from six to twelve inches long, hollow, and shaped something like a
trumpet, while the aperture of the apex is formed almost precisely in
the same manner as those of the plants previously described. A broad
wing extends along one side of the leaf, from the base to the opening
at the top; this wing is bound or edged with a purple cord, which
extends likewise around the cup. This cord secretes a sweet fluid, and
not only flying insects, but those also that crawl upon the ground,
are attracted by it to the plants. Ants, especially, are very fond of
this fluid, so that a line of aphides, extending from the base to the
summit of a leaf, may frequently be observed slowly advancing toward
the orifice of the cup, down which they disappear, never to return.
Flying insects of every kind are equally drawn to the plant; and
directly they taste the fluid, they act very curiously. After feeding
upon the secretions for two or three minutes they become quite stupid,
unsteady on their feet, and while trying to pass their legs over their
wings to clear them, they fall down.
It is of no use to liberate any of the smaller insects; every fly,
removed from the leaf upon which it had been feeding, returned
immediately it was at liberty to do so, and walked down the fatal cup
as though drawn to it by a species of irresistible fascination.
It is not alone that flies and other small insects are overpowered by
the fluid which exudes from the cord in question. Even large insects
succumb to it, although of course not so quickly. Mrs. Treat says: "A
large cockroach was feeding on the secretion of a fresh leaf, which
had caught but little or no prey. After feeding a short time the
insect went down the tube so tight that I could not dislodge it, even
when turning the leaf upside down and knocking it quite hard. It was
late in the evening when I observed it enter; the next morning I cut
the tube open; the cockroach was still alive, but it was covered with
a secretion produced from the inner surface of the tube, and its legs
fell off as I extricated it. From all appearance the terrible
_Sarracenia_ was eating its victim alive. And yet, perhaps, I should
not say 'terrible,' for the plant seems to supply its victims with a
Lethe-like draught before devouring them."
If only a few insects alight upon a leaf, no unpleasant smell is
perceptible during or after the process of digestion; but if a large
number of them be caught, which is commonly the case, a most offensive
odor emanates from the cup, although the putrid matter does not appear
to injure in any manner the inner surface of the tube, food, even in
this condition, being readily absorbed, and going to nourish the
plant. In fact, it would seem that the _Sarracenia_, like some
animals, can feed upon carrion and thrive upon it.
In instances in which experiments have been made with fresh, raw beef
or mutton, the meat has been covered in a few hours with the
secretions of the leaves, and the blood extracted from it. There is,
however, one difference between the digesting powers of the leaves
when exercised upon insects or upon meat. Even if the bodies of
insects have become putrid, the plant, as has already been stated, has
no difficulty in assimilating them; but as regards meat, it is only
when it is perfectly sweet that the secretions of the leaves will act
upon it.
The pitcher plant undoubtedly derives its principal nourishment from
the insects it eats. It, too--unlike most other carnivorous plants,
which, when the quantity of food with which they have to deal is in
excess of their powers of digestion, succumb to the effort and
die--appears to find it easy to devour any number of insects, small or
large, the operation being with it simply a question of time. Flies,
beetles, or even cockroaches, at the expiration of three or four days
at most, disappear, nothing being left of them save their wings and
other hard, parts of their bodies.
The _Sarracenia_ is, indeed, not only the most voracious of all known
species of carnivorous plants, but the least fastidious as to the
nature of the food upon which it feeds.--_W.C.M., Nature._
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