“PLANT EATS FOUR FLIES”
Perhaps to most of us this sounds like an excerpt from Ripley’s column. If the statement read, “Four insects eat plant!”, it would arouse no curiosity because we know most insects as well as many animals are herbivorous, that is, they live on herbs or plants.
The fundamental difference between plants and animals lies in their method of obtaining food. Did you ever hear a plant eating? Have you ever rested in the stillness of a large forest and wondered how so many huge trees could be constantly eating or drinking noiselessly? The plants quiet method of absorbing dissolved minerals and water stands in sharp contrast to the munching, grinding, gnawing of animals. Even more remarkable is the fact that there are certain plants which eat insects, and this mastication, too, is inaudible.
There are only five members of this carnivorous (animal-eating) group of plants—the Sundew, Bladderwort, Pitcher-plant, Buttervort. and the Venus Flytrap. They are commonly called insectivorous plants because insects serve as the major part of their diet. Careful observation, however, has proved that they are carnivorous rather than insectivorous, as their food is not limited to insects but also includes many small worms, spiders, and microscopic animals.
By this time, you undoubtedly wonder how these plants catch these small creatures. Have they means of locomotion by which they pursue their prey? Have they mouths by which they capture and eat their victims? Neither is the case, but they do have a means of enticing their prey and an ingenious trap of their own. Let us carefully observe the various means of ensnarement.
At the edge of a bog we see a small herb about the size and shape of a strawberry plant, whose oval leaves resemble a pin-cushion covered with pins shining brightly in the morning sun. Upon closer investigation we find that these many pin-like projections are sensitive hairs capped with a globe-like gland which secretes a glistening, sticky fluid similar to the droplets of morning dew from which it derives its name—the Sundew. Thinking that the sparkling leaves are flowers, insects alight upon them, but immediately the sticky secretion of the hairs imprisons them. While they struggle desperately for freedom the neighboring tentacles being stimulated bend in closely upon them. The glands then produce a digestive ferment which dissolves the insect so that it can be absorbed by the leaves, while the remains are removed by the wind. Of the ninety species of sundew, only a few are found in our country, for most of them are native to Australia.
On the surface of ponds and streams one may find a Bladderwort drifting along. This filamentous plant sometimes grows to a length of 3 feet. In spite of the fact that it lacks roots the usual source of gaining food, it possesses many small pear-shaped bladders which capture microscopic animals. Although various theories have been propounded to explain the method of seizure, only recently has this mystery been satisfactorily solved.
Long ago, Darwin had suggested that minute animals, while searching for food or protection, found their way through the small opening into the bladder. Later, a Swiss scientist, while distributing some specimens to one of his classes for laboratory work, heard a peculiar ticking. After examination, he noticed that these small bladders operated on the same principle as the medicine dropper or the fountain-pen: suction. His explanation was that the insect, when coming into contact with the sensitive bristles guarding the opening of the bladder stimulated the bladder to expand and suck in the water which often contained many tiny animals. To prove his theory of suction, he placed a hair in the opening and discovered that it no longer functioned. Further experimentation proved that pricking the bladder with a pin destroyed the power of suction. In both cases the damaged bladders were unable to obtain any more food as insects ceased to enter the bladders. Thus, Darwin’s theory of the voluntary entrance of animals was disproved.
A third interesting example is the Pitcher-Plant, sometimes found in the Michigan bogs. Its reddish-green leaves are shaped like a pitcher. Inside of the upper edge of the pitcher is a layer of sweet-scented nectar which attracts the insect. Eagerly the hungry insect investigates the source of this savory substance, only to find itself lured into a watery trap below. Futile are its efforts of escape for the slippery walls provide no foothold. Soon the pool of digestive juices at the bottom of the pitcher dissolves its body. Another insect has met its “Waterloo”.
The Butterwort—another varied form of this special group of plants —possesses very greasy leaves upon which the victim struggles valiantly for release as he slides to and fro. These very efforts of escape stimulate the leaves to curl inward and, thus, entrapping it while the secretions of the leaves dissolve the helpless body.
For our last example we must travel to a small section in North Carolina, where we can get a glimpse of the Venus Fly-Trap. It has peculiar hinged leaves, resembling the shape of a butterfly’s body. On the upper surface are six, jointed, sensitive hairs. When an insect touches one of these hairs the leaf immediately closes and comb-like projections on the margins interlock, thus preventing all means of escape. Special glands on the surface of the leaf produce digestive juices which dissolve the prisoner’s body.
Why do these plants eat insects and other small animals? Most of them are found in bogs or similar locations where the soil lacks nitrogen — an essential element for growth. The bodies of these small creatures contain these necessary nitrates, and so, by eating them, the carnivorous plants can obtain what the roots fail to provide.
In order to prove that nitrogen was so important, Darwin covered two plants with gauze to prevent the entrance of any insects. One of these he supplied with nitrates in the form of fertilizer, while the other was unfed. The result was that the former flourished, while the latter wilted and died. In another experiment, he placed particles of meat, cheese hard-boiled egg, glass, and other bits of food into different Venus Fly-Trap plants. When he investigated the outcome, he found that the meat, cheese and egg particles were dissolved, while the rest were untouched, illustrating that only those foods containing nitrogen could be digested and were useful.
Even though these five types of plants have a very small root system, and are located in unfertile soils, they can beautifully reflect the providence of the great Designer.