X | Some Wonders of Plant Life
We usually think of plants as quite harmless things, almost wholly at the mercy of the animal creation. This, however, is only one side of the story, for quite a number of plants have a very cunning plan whereby they entrap flies and other insects. The ingenuity with which these plants lure their victims on to death is simply amazing. Everything is done to tempt the creature to visit the death traps of the plants, and, on the other hand, no means are spared to make an escape impossible.
The Most Cruel Plant in the World
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.
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. | Once below the inside edge, escape is almost impossible. Pitchers have been found almost full of flies and other insects. |
| Absorbed in the delights of feasting on the nectar of the Nepenthes, the insect wanders with fatal ease down the fluted rim. | 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.
The Strange Habits of the Nepenthes
Scattered over the tropics of the old world there is a remarkable group of plants known as Nepenthes. Many of these are of a climbing habit, rooting in bark crevices where a little moist soil may have collected. To augment their food supply they have produced pitchers, which in some species are of great size. Indeed, in one kind of receptacles will hold as much as two quarts of water. In all cases these pitchers have a thick, corrugated rim, and it is this which plays a big part both in the luring and the capturing of the insects. On this rim, as well as on the lid of the pitcher, there are honey secreting glands, and these, of course, make the strongest appeal to hungry insects.
Absorbed in the delights of the feast, the insect wanders with fatal ease down the fluted rim. Once below the inside edge of this, escape is almost impossible, for the border is adorned with sharp, teeth-like processes, all pointing downward to the pit of destruction. Moreover, the inside walls of the pitcher are specially smoothed with a wax-like secretion, which makes climbing up a very difficult feat. Even insects with wings seem to find a great difficulty in making good their escape.
The pitchers of the Nepenthes are usually about half filled with fluid; this is not entirely collected rain or dew, but is largely formed by a definite secretion of the plant. Into this fluid the exhausted insect tumbles sooner or later, there to end miserably among a mass of drowning victims. It has been definitely proved that this fluid is an acid secretion—not unlike the digestive juices of an animal—which enables the plant to extract the nutriment it needs from the bodies of its victims.
The Nepenthes Catch Even Mice and Birds
It is in connection with the fluid contained in the pitchers of the Nepenthes that these plants catch much larger prey than insects. In the tropics it is not always an easy matter for birds and other small animals to secure a drink readily. The half-filled pitchers entice many a small creature to creep over the fluted rim in order to secure a draught of the fluid, which is not unpleasant to the taste. Now and again the venturesome visitor loses his hold and tumbles into the pitcher. Even in the case of mice and small birds the pitcher proves a veritable death-trap. The slippery sides are almost insurmountable, while the sharp hooks round the rim still further check an escape. Sooner or later the victim falls back into the fluid and is drowned. Strange as it may appear, after such a capture the plant grows vigorously, for the decaying body of its victim is rich in just the food material of which it stands in need.
The Death Pitcher of the Sarracenias
A very singular group of plants, the Sarracenias, are quite common in the bogs of North America. These are of an elegant shape, and may be as much as one foot or two feet in height. Nearly always they are highly colored, and altogether so attractive do they appear that insects of all kinds simply crowd to them. On arrival at the lip of the pitcher, the insects find a feast of honey spread out for their delectation. With almost devilish ingenuity this becomes sweeter and more plentiful the farther down into the pitcher one traverses. At a certain point, however, the nectar ceases, and the insect thinks that he will retrace his steps. But although it has been easy enough to go down, it is almost impossible to get back, for the surface of the inside of the pitcher is thickly covered with sharp bristles, all pointing downward.
Some flying insects may escape, but even these do not find it easy, as witness the fact that the plant often catches a large number of winged creatures. In the lower part of the Sarracenia pitcher a fluid is secreted, and it is into this that the creatures ultimately fall, and, of course, perish. How successful are the Sarracenias in their insect-catching may be gathered from the fact that pitchers have been discovered well nigh full of flies and other small creatures.
A Plant with Prison Windows
The California Darlingtonia seems to have been specially devised for the securing of winged creatures. The plant is most singular in appearance, and the upper part of the pitchers bear a remarkable resemblance to the head of a snake. Part of the hood and also the two protruding leaves are gaily colored in crimson. It should also be noted that the upper portion of the hood is adorned with transparent patches, like so many little windows. Now, the only opening into the pitcher of the Darlingtonia is quite a small hole on the under side of the hood. As in the case of the other pitcher plants, the orifice of this hole is freely supplied with honey, and this extends well into the interior of the receptacle.
Owing to the attraction of the little windows, which have been already mentioned, the flies do not attempt to get out of the hole to the extent which might be supposed. The light streaming through the transparent spaces seems to convince the insects that in that direction lies the path to freedom. At all times it is possible to see perhaps a dozen flies bobbing against the windows in a vain endeavor to escape. Finally, wearied to death by their hopeless endeavors to escape, the insects fall down into the lower part of the pitcher and become suffocated by the fluid it contains.
An Australian Plant with Two Kinds of Leaves
A curious little Australian plant which has adopted a very similar plan of fly catching to that to be seen in the Nepenthes is the Cephalotus. One singular feature about this Australian pitcher plant is that it produces quite ordinary leaves in addition to the highly specialized fly-catching ones.
Plants That Kill Even the Powerful Lion
The Martynias of South America produce fruits with hooks sometimes five or six inches in length, [172] which get imbedded into the flesh of animals. The African Grapple-plants (Harpagophyton procumbens) are even worse in the amount of suffering which they cause; thousands of antelopes, goats, and other creatures are lamed by them every season. The seed vessel of this plant is provided with a large number of curved hooks by which it attaches itself to the coats or hoofs of animals and is thus transported from place to place. It has been known to choke and cause the death of lions.
| The pretty little parachute-like device of the Dandelion seed which helps to waft it over a wide area. It often rises to a height of thirty feet, and is wafted many miles away. | The Willow Herb produces an enormous number of flying fruits. These often sail away in masses and are carried for a great distance over the countryside, to take root in a new location. | The seed of the Sycamore is provided with a long wing. These wings revolve quickly when the heavy seed is falling, prevent a rapid decent, and help to scatter them. | |||
| The head of a seeding Dandelion. Observe the enlarged view of one of the parachutes above. | When the fruits of the Coltsfoot are ripe the smallest puff of air disperses the seed far and wide. | ||||
How Plants Travel
Many plants provide their seeds with an apparatus which forms a singularly effective flying machine. Some of these are among the most beautiful and ingenious contrivances in the plant world.
Nature’s Aviators and Seed-Sowers
By far the commonest method of ensuring a wide distribution of a seed is that in which the object is attached to some light, feathery substance which prevents a speedy falling. Of this there is no better instance than the common dandelion, which at seed time produces the handsome “clock” so prized by the children.
Here each seed is attached to a feathery process which plays the part of a parachute. On a dry day, when the dandelion heads are parting with their fruits, we may see how well the scheme works. Each puff of wind releases a few of the seeds, and these, unlike the ordinary parachute with a load, are so light that they rise upwards on the air currents.
Curiously enough, the fruits seem to travel farther when the breezes are light, and a very rough wind blows them back to earth, where they may catch in the grass or become damaged. Thus, like the airman, the dandelion seed stands the best chance of a safe journey when the weather is not too boisterous.
A very similar arrangement is to be seen in the case of the goat’s-beard fruit and that of the coltsfoot, which, by reason of its flying device, secures a very wide distribution.
The Willow Also Produces Flying Seeds
After flowering the Willow Herb develops long, pod-like processes. During damp and stormy weather these pods remain tightly closed. On a day when the air is dry and the breezes are light, the sides of the case split open and reveal a prodigious number of perfect flying machines. The seed itself weighs a mere trifle, and to this is attached a beautiful arrangement of feathery hairs. The whole thing is so well adapted for an aërial voyage that it mounts rapidly upward on the faintest puff of air. It should be here explained that by experiment it has been shown that the air currents tend to move upward. So light are some of these flying fruits that they often rise to an immense height. It is not an uncommon thing for them to be found on mountains thousands of feet above sea-level.
Of course, many foreign seeds have remarkable flying appendages. That of the South African Stapelia has a vast mass of fluffy hairs which will support it on quite a long aërial voyage. In the case of the cotton plant man has turned to good account the hairs by which the seed flies.
Seeds of the Sycamore a Different Type of Flying Machine
In a large number of cases the conveyance of the seeds to a distant point is accomplished by the adoption of the screw-propeller principle. An excellent example of this is to be seen in the fruits of the sycamore. Here the actual seed is large and heavy, but it is attached to a wing-like expansion. When the fruit falls from the tree the wing revolves with great rapidity, very much on the lines of a propeller blade. This has the effect of controlling the rate of fall, so that the whole contrivance is carried to some distance before the seed is actually brought to earth.
Plant Travelers on Land
Some kinds of touring plants send out long trailing stems to search for fresh rooting places. A little Alpine saxifrage is curious in this respect, for the plant will traverse over many feet of barren rock to reach a suitable position. Directly the shoot touches the soil, a new plant is formed, and as this grows up, the connection between it and the parent is severed. A kind of lily has an even more singular way of traveling about. Here, after the plant has flowered, buds arise on the stems which bore the blossoms. Eventually they take root in fresh positions. This plant if left alone would rapidly cover many yards with its offspring, and this without setting a single seed.
A strange group of plants are those which actually break themselves in pieces in order to pursue their journeys abroad. A plant belonging to the Houseleek order (Sempervivum soboliferum) is remarkable in this respect. The species naturally finds its home in the crevices of rocks, and at a certain stage in its development numerous little ball-like offshoots are produced. In the early days these are kept at home by the stems by means of which they are attached to the parent plant. Eventually these attachments shrivel up and the offshoots go rolling away over the rocks often much helped in their journey by the wind. A considerable distance may be traversed before a little ball finds a resting-place in some niche.
HOW THE CACTUS PROTECTS ITS FLOWERS
How the Plants Defend Themselves
It is well-known to every intelligent observer that plants are menaced by a host of enemies. Though the plant cannot take up the aggressive to any extent, the weapons which it employs in its own defense are of an exceedingly efficient nature. In their way they are quite as effective as anything that animals employ in their battle for existence.
Among the commonest defenses of the plant are spines, thorns and prickles. In the sloe (Prunus spinosa), for example, the spines are modified branches; in gorse (Ulex Europæus) they are branches and leaves; and in cacti the green parts are thickened stems and the spines reduced leaves; while in holly (Ilex aquifolium) the prickly leaves answer the purpose of spines. The stinging hairs of the nettle which exude an irritating acid when touched are a familiar example of protection against vegetarian animals.
The way in which seeds are protected by spines is well illustrated in the case of the Sweet Chestnut. Here it would be a very knowing animal that could open one of the cases before they split naturally with the ripening of the seed.
How the Cactus Defends Its Life
There are few plants so well armed as the Cactus, the evident design of which is to conserve its moisture. This is accomplished in several ways. Of course, the very shapes of the plants are all in their favor. Being either round, globular, or cylindrical, they offer a limited surface to the dry air inconceivably less than a plant of the same size bearing a quantity of leaves. The thick skins, too, play a big part in keeping in the moisture, and many kinds of cacti, such as that known as Old Man’s Beard, are covered with dense masses of hair.
Many of these succulent desert plants grow to a great size. Thus the Giant Cactus sends up a tall column, often with only a very few branches, which may be eighty or even one hundred feet in height.
Curiously enough, some cacti produce the most beautiful flowers, blossoms without rival in the whole world. The various kinds bear flowers of every conceivable shade except blue, and the blooms are often of an immense size. It is not unusual for the blossoms to measure eighteen inches, or even two feet, across.
Living as they do in arid regions, cacti are peculiarly liable to be attacked by thirsty animals. Now, a common mode of defense is the covering of the plant with sharp spines. These spines are so arranged that they completely shield the juicy stem from any possibility of attack, it is said that on occasion Mexican ponies will try to knock a cactus to pieces with their heels when they are thirsty. More often than not the animals suffer cruelly for their temerity by being severely pricked.
In much the same way the Aloes and Agaves are protected, so that a hedge of these plants when placed round a field, is better than the most perfect barbed wire fence.
The American Agave, or “Century Plant”
This plant is remarkable for its beauty, and grows to a height of twenty to thirty-five feet. It was long popularly supposed to bloom only once in a century; hence the name. Though this is a mistaken idea, the vegetative growth of the plant is many years. The plant produces flowering stems, sometimes several feet in height, ultimately terminating in a large panicle of flowers and dying of the effort. A single plant may produce five thousand flowers, so that the ground beneath is wet with the honey distilled by them. The fiber of the leaves was used by the ancient Mexicans for paper parchment, and is now largely exported for that purpose and for cordage.
The Curious Mistletoe, a Robber Plant or Parasite
The mistletoe is one of the most interesting of the parasite plants. It grows on various trees, and is celebrated on account of the religious purposes to which it was consecrated by the ancient Celtic nations of Europe. It is a small shrub, with oblong, somewhat leathery leaves, and small yellowish-green flowers, the whole forming a pendent bush, covered in winter with small white berries, which contain a glutinous substance. It is common enough on certain species of trees, such as apple and pear trees, hawthorn, maple, lime, and other similar trees, but is very seldom found on the oak. Its roots penetrate into the substance of the tree on which it grows, and though it may live for forty years, it finally kills the branch supporting it.
In days of old the mistletoe was looked upon with awe as a mysterious and wonderful plant. The ancient Druids held it sacred, and cut it down with a golden sickle with all sorts of strange, mystic rites. It was the symbol of peace and friendship; and that is why we hang it up at Christmas time, and when two people meet under its green leaves, they are expected to “kiss and be friends.”
A Plant That Grows in Snow
Strangest of all the plants is the Soldanellas, a small species which exists on the lower slopes of the Alps. When the flower stems are in their most active state of growth they release a considerable amount of heat. In this way they will bore a course up through a thick coating of ice and snow to the light and air above, when by some means the plant is aware that the spring has arrived. There seems to be something more wonderful in this than can be explained by mere mechanical causes. Indeed, the sympathy of the plant with its surroundings is surely one of those mysteries which are as inscrutable as life itself.
The Primary Use of Liquid Rubber to Plants
The grubs of many beetles live in wood, upon which they feed. This probably gives a clue to the primary use of the important commercial substances india-rubber and guttapercha, which are the dried sticky juices of various shrubs and trees growing in hot climates. Beetles of the wood-boring kind, which seek to pierce and lay eggs in such plants, are liable to be snarled and killed by the viscid fluids which ooze out.
Arums, and various other plants, ward off the attacks of snails and slugs in a rather curious way The outer parts of their stems and leafstalks contain bundles of excessively sharp crystals (raphides), composed of oxalate of lime. These pierce the soft mouths of snails and slugs like so many needles, conveying a lesson which usually needs no repetition.
STRANGE LIFE HABITS OF UNUSUAL PLANTS
The Giant Cactus of the American Desert
These plants are little more than succulent stems covered with a thick skin which retains the moisture of the juicy shoot.
The Century Plant
The Century Plant is a native of Mexico, and is remarkable for the long intervals between the blooming periods—once erroneously thought to be 100 years.
CHRISTMAS ROSE IN WINTER
In defiance of the weather a few plants elect to come into bloom right in the middle of winter. The most striking of these is the Christmas Rose, or Hellebore. The flowers of this plant are protected by the encircling sepals, and are fully able to hold their own until the approach of a more favorable season.