You may have heard that the life led by plants is quite as fascinating in its way as the life of animals. The passage that follows introduces you to one of the wonders of plant life with which many people are not familiar. It tells you how a number of plants have devised ways of living at the expense of members of the animal kingdom.
It is a very ordinary thing to hear of animals eating plants, but have you ever heard of plants setting traps for animals and then sucking them to death? It sound very horrible, yet the plants that set these traps are most interesting, and the creatures they catch are usually flies that we ourselves kill if we have the chance.
Three of these plants grow wild in the British Isles. They are usually found on the colder, boggy moorlands of Scotland, Ireland, and Wales. In England, they are to be found, but only one of them, Sundew, is common.
The leaves of sundew from a rosette pressed back upon the ground. Each leaf is round with rather a long stalk and is covered with club-shaped red hairs. There are about two hundred hairs on each leaf, and at the end of each is a bright-yellow glistening drop, which looks like dew and gives the plant its name. From the center of the rosette, a flower stalk rises in summer, and it is those plants, which catch the most flies that make most flowers and seeds.
The leaves with their red hairs are the flytraps. The glistening drops attract insects in search of nectar, but when they alight, they find the yellow drops so sickly that they cannot get away. They may struggle, but in doing so they touch more red hairs and get more entangled. The wonderful thing about these hairs is that if rain or sand falls upon them, they do not move; yet, when anything fit for food touches them, they begin to curl over and pin it down. Sometimes we wonder whether plants can feel and whether they can send messages from one part to another, as we can along our nerves. Certainly, it is very difficult to understand why all the tentacles of a sundew leaf curl over towards the prisoner, whether the fly has touched them or not. Yet this is what happens. The poor fly is suffocated by these hairs and the juice, which they pour bovver it. It takes about two days for the sundew to digest a fly, and when the tentacles open out once more, all that remains are the dry wings and skin. The leaf, too, is dry for a short time, so that wind and rain can clear away the remains before the leaf sets about attracting another fly.
The Venus’ flytrap is a North American plant, which is similar to sundew. The leaves are arranged in a similar rosette, but each one consists of two semi-circles fringed with sharp teeth, at the end of a flattened stalk. In the centre of each half, there are three more bristles. As soon as an insect touches one of these bristles, the two halves of the leaf snap together like a trap and enclose it.
If we visit Kew or any other botanical garden with hothouses, we shall see not only sundew growing, but also some other insectivorous plants called Pitcher Plants. These plants come from North America and Madagascar. Each plant bears perhaps two dozen pictures, each of which reminds us somewhat of a Dutchman’s pipe. The bowl is formed from part of the leaf and rises from the end of a long, dropping stem, while a small leaf like lid protects the opening at the top from rain.
The pitcher is streaked with red and green and is very attractive, but insects on the lookout for nectar are attracted by quantities of this sweet liquid, which they find on the outside of the pitcher and at the top, round the rim. Once at the top, curious insects peer inside and see more nectar on the sides of the pitcher. In their greed, they climb down towards it. Nothing stops them. The pitcher is certainly lined with long hairs, but they all point downwards and assist the fly in reaching the nectar. Once satisfied, however, the fly tries to return and finds that those long hairs are pointing towards him. They helped him to descend, but now they are turned against him. He struggles to climb and now finds that the sides of the pitcher are very slippery. At last, in his struggles to climb, he slips and falls down to the bottom of the pitcher into the water which has collected there? This is no ordinary water. It is acid and very like the juice in our stomachs, which digests our food. So the poor fly is drowned and digested and his juice goes to feed the pitcher plant.
We usually find insectivorous plants growing where the soil is very poor and especially lacking in that kind of manure, which we call, nitrates. Some of them can live without the insects, but they do not flourish, for the insects provide them with the nitrate food, which is missing from the soil.
If these plants lived entirely upon the insects or could not live without them, we should call them parasites. There are many such plants, but they are not plants, which set traps for insects, and if they do live on animal food, they usually wait until the animals are dead.