Stories of the Universe

The Plants

The following has been prepared and presented purely for its historical content and entertainment value. It is full of errors amoung others Fig. 11 labeled as an Australian pitcher plant is actualy a Sarracenia. Take this with a few grains of salt. I hope you find it as much fun as I did.

Chapter V. "How Plants Drink"

Beginning near the top of page 63 and ending on page 68

Moreover, nature sometimes even goes in for deliberate manuring. Plants like buttercups and daisies, that live in ordinary meadow soils, to be sure, get enough nitrogen and sulphur and other such constituents from the mould in which they are rooted. But in very moist and boggy soils there is generally a lack of these necessary earth given elements of protoplasm; and natural selection has therefore favoured any device in the plants which grow in such places for obtaining them elsewhere. This they do as a rule by catching insects, killing them, and sucking their juices, and using them up as manure for manufacturing their own protoplasm and chlorophyll. Our pretty little English sundew is one of these cruel and perfidious plants.

Its leaves are round, and thickly covered with small red hairs, which are rather bulbous at the end, and very sticky. The bulbous expansions, in point of fact, are small red glands, which exude a viscid digestive liquid. When a small fly alights on the leaf, attracted by the smell of the sticky fluid, he is caught and held by its gummy mass; the hairs then at once bend over and clutch him, pouring out fresh slime at the same time, which very shortly envelops and digests him. In the course of a few hours the leaf has sucked the poor victim's juices, and used them up in the manufacture of its own protoplasm.

Many other insect-eating plants exist in the marshy soils of other countries. One of the best-known is the Venus's fly-trap of tropical or sub-tropical North America. In this curious plant the leaf is divided into two portions, one of which forms a jointed snare for catching insects. It is hinged at the middle; and when the fly lights upon it, the two edges bend over upon him, and the bristles on the margin interlock firmly. As long as the insect struggles they remain tightly closed; when he ceases to move, and is quite dead, they open once more, and set their trap afresh for another insect. A great many such carnivorous and insectivorous plants are now known: and in almost every case they inhabit places where the marshy and waterlogged soil is markedly wanting in nitrogen compounds. Insect-eating leaves are thus a device to supply the plant with nitrogen by means of its foliage, in circumstances where the roots prove powerless for that purpose.

Simpler forms of the same sort of habit may be seen in many other familiar plants. Thus our English catchflies and several other of our common weeds have sticky glandular stems, which exude a viscid secretion, by whose aid they catch and digest flies. This is the beginning of the insect-eating habit, more fully evolved by natural selection in marsh plants like sundew, and especially in larger subtropical types like the Venus's fly-trap. If you collect English wild-flowers you will soon perceive that a great many of them have sticky glands on the summit of the stem, near the flowering heads; and this is useful to them, because the flowers and seeds are particularly in want of nitrogenous matter for the pollen and ovules and the development of the seed. In short, though plants get their nitrogen mainly by means of the roots, they often lay in a supplementary store by their stems and their foliage.

Our common English teasel shows us the beginnings of another form of insect-eating, which is highly developed in certain American and Asiatic marsh plants. The leaves of teasel grow opposite one another, joining the stem at the base, so as to form between them a sort of cup or basin, which will hold water. If you look close into this water you will find that it is often full of dead midges and ants; and the plant puts forth long strings of living protoplasm into the water. into the water, which suck up the decaying juices of these insects, and use them in the manufacture of more protoplasm and chlorophyll. In this case, water is used both as a trap and as a solvent; the insects are first drowned in the moat, and then allowed to decay and digest themselves in it.

Teasel, however, is but a simple example of this method of insect-catching. Several American marsh-dwellers, collectively known as pitcher-plants, carry the same device a great deal further. They are far more advanced and developed water-trap setters. The Canadian side-saddle plant allures insects to its vase-shaped leaves, which are filled with sugar and water. This is just the same plan which we ourselves employ to catch flies when we trap them in a glass vessel by means of a sweetened and sticky liquid. The pitchers are formed by leaves which join at the edges; they are attractively coloured, so as to allure the flies; and they secrete on their walls a honeyed liquid, which entices the victim to venture further and further down the fatal path. But the inner sides of the vase are set with stiff downward-pointing hairs, which make it easy to go on, but impossible to crawl back again. So the flies creep down, eating away at the sticky sweet-stuff as they go, till they reach the bottom and the hungry water, when they fall in by hundreds, and are drowned and digested. I have found these plants often by the sides of Canadian bogs, with a whole seething mass of festering and decaying insects filling up every one of their murderous vases. Other pitcher-plants are found in Australia ( Fig. 11 )

The Nepenthes of the Malayan Archipelago is a still more remarkable water-trap insect-eater, in which the pitcher is formed by a curious jug-like prolongation at the end of the leaf (Fig. 12). It is provided with a lid, and its rim secretes a sticky sweet liquid. Insects that enter the jug are prevented from escaping by strong recurved hooks; and these hooks are so powerful that at times they have been known even to capture small birds which had been incautiously entered. This may seem curious, but it is not odder than the fact that our own English bladderwort, a water plant with pretty yellow flowers, which grows in sluggish streams, has submerged bladders that supply it with manure, not only from the water-beetles, larvae, and other insects, but also from trout and other and other young fry of fresh-water fishes. I may add that while the sundew and other live-insect catchers have to digest their prey, the water-trap makers save themselves that additional trouble and expense by macerating and soaking it till it reaches the condition of a liquid manure, ready dissolved for absorption, and easy to assimilate.

Thus we see that while roots are the chief organs for absorbing nitrogenous matter, they are often supplemented in special circumstances by leaves and stems....