Kitabı oku: «Birds and All Nature, Vol. VI, No. 1, June 1899», sayfa 5

A FLY-CATCHING PLANT

WILLIAM KERR HIGLEY,

Secretary of The Chicago Academy of Sciences

 
Queen of the Marsh, imperial Drosera treads
Rush-fringed banks, and moss-embroidered beds.
 

– Erasmus Darwin, in The Botanic Garden, 1789.

SOME of the most interesting forms of nature are not the most showy and are not easily observed by the untrained eye. Many of their characteristics can only be known by carefully conducted investigations, both in the field and in the laboratory.

The advance of science has shown us that it is as natural for some plants to obtain much of their nourishment from the animal world, by a true process of feeding, as it is for animal forms to obtain their sustenance, either directly or indirectly, from the vegetable world.

There are many species among the lower orders of plants that are well known animal parasites, but there are also, among our more highly organized flowering species, forms that improvise a stomach and secrete an acid fluid for the digestion of nitrogenous food which is afterwards absorbed and used in tissue building. These are in no sense of the term parasites.

Such a plant is our common round-leaved sundew (Drosera rotundifolia, L.). The generic name Drosera is from the Greek, meaning dew.

This rather insignificant, but pretty little plant is distributed nearly throughout the world, and is usually found in bogs, or in wet sand near some body of water. The flower stalk is seldom more than six or eight inches in height and bears very small white or pinkish-white flowers.

The interesting feature of this species, however, lies in the rosette of about five or six leaves growing from the base of the stem. These leaves lie upon the ground and are usually about one-fourth to one-half of an inch in length, and are generally nearly orbicular in form. The upper side is covered with gland-bearing tentacles. The glands are covered by a transparent and viscid secretion which glitters in the sunlight, giving rise to the common name of the plant. There are usually over two hundred tentacles on each leaf and, when they are not irritated, they remain spread out. The viscid fluid of the glands serves as an organ of detention when an insect lights upon the leaf. The presence of an insect, or, in fact, any foreign matter, will cause the tentacles, to which it is adhering, to bend inward toward the center of the leaf and within a very short time all the tentacles will be closed over the captured insect, which is soon killed by the copious secretion filling its breathing apparatus.

Though these sensitive tentacles are not excited by either wind or rain they are by the repeated touchings of a needle, or any hard substance. It is said that a fragment of hair weighing but 1-78,740 of a grain will cause a perceptible movement.

By experiment it has been shown that a bit of hard-boiled egg, or a fragment of meat as well as an insect will cause not only an inflection of the tentacles but also of the edges of the leaves, thus forming an improvised stomach, the secretion of the glands then increasing and becoming acid. At this stage the secretion is not only capable of digesting but is also highly antiseptic.

This power of digesting and absorbing nitrogenous food is absolutely necessary to the existence of the sundew, for it usually grows in a poor soil and its few and not greatly elongated roots are of little service except to absorb water, of which it needs a large amount for the production of the copious secretion. Specimens may be developed by planting in moist cotton and furnishing with plenty of water.

The length of time that the tentacles will remain inflected depends on the vigor of the leaf and the solubility of the material causing the excitement. The time varies from one to seven or eight days.

Easily dissolved and readily absorbed food in too large an amount seems to cause overexcitement and overtaxation, and frequently results in the death of the leaf.

The large number of insects, especially flies, captured by these plants would lead one to believe that they are attracted by the odor of the plant, or the purplish color of the tentacles, rather than by the desire to use the leaves as a resting-place.

The sundew belongs to the natural order Droseraceæ. This contains about one hundred and twenty-five species, of which one hundred and ten belong to the genus Drosera, and are chiefly natives of Australia, though the round-leaved species is common throughout the United States, Europe, and Asia.

Closely related to the sundew is the Venus fly-trap (Dionæa muscipula, Ellis). This is a native in the eastern part of North Carolina only.

The leaf of this plant is provided with two lobes, which close quickly when the sensitive hairs, which are situated on the upper surface of the leaf, are irritated by an insect. The acid secretion flows out and the leaves remain closed till digestion and absorption are completed.

Dr. Asa Gray has referred to this species as "that most expert of fly-catchers."

TREES AND ELOQUENCE

W. E. WATT

FORTY years in the pulpit of Plymouth Church in Brooklyn Henry Ward Beecher stood and poured forth a stream of eloquence which shook the world. During the stress of civil war he stemmed the current of English sentiment with his peculiar powers and brought about a change of feeling which was the salvation of our Union. This greatest of our pulpit orators was a lover of trees, and some of his finer passages were inspired by them.

Without doubt, better trees there might be than even the most noble and beautiful now. I suppose God has, in his thoughts, much better ones than he has ever planted on this globe. They are reserved for the glorious land. Beneath them may we walk!

To most people a grove is a grove, and all groves are alike. But no two groves are alike. There is as marked a difference between different forests as between different communities. A grove of pines without underbrush, carpeted with the fine-fingered russet leaves of the pine, and odorous of resinous gums, has scarcely a trace of likeness to a maple woods, either in the insects, the birds, the shrubs, the light and shade, or the sound of its leaves. If we lived in olden times, among young mythologies, we should say that pines held the imprisoned spirit of naiads and water-nymphs, and that their sounds were of the water for whose lucid depths they always sighed. At any rate, the first pines must have grown on the seashore, and learned their first accents from the surf and the waves; and all their posterity have inherited the sound, and borne it inland to the mountains.

I like best a forest of mingled trees, ash, maple, oak, beech, hickory, and evergreens, with birches growing along the edges of the brook that carries itself through the roots and stones, toward the willows that grow in yonder meadow. It should be deep and sombre in some directions, running off into shadowy recesses and coverts beyond all footsteps. In such a wood there is endless variety. It will breathe as many voices to your fancy as might be brought from any organ beneath the pressure of some Handel's hands. By the way, Handel and Beethoven always remind me of forests. So do some poets, whose numbers are as various as the infinity of vegetation, fine as the choicest cut leaves, strong and rugged in places as the unbarked trunk and gnarled roots at the ground's surface. Is there any other place, except the seaside, where hours are so short and moments so swift as in the forest? Where else except in the rare communion of those friends much loved, do we awake from pleasure, whose calm flow is without a ripple, into surprise that whole hours are gone which we thought but just begun – blossomed and dropped, which we thought but just budding?

Thus do you stand, noble elms! Lifted up so high are your topmost boughs that no indolent birds care to seek you, and only those of nimble wings, and they with unwonted beat, that love exertion and aspire to sing where none sing higher. Aspiration! so heaven gives it pure as flames to the noble bosom. But debased with passion and selfishness it comes to be only Ambition!

It was in the presence of this pasture-elm, which we name the Queen, that we first felt to our very marrow that we had indeed become owners of the soil! It was with a feeling of awe that we looked up into its face, and when I whispered to myself, "This is mine," there was a shrinking as if there were sacrilege in the very thought of property in such a creature of God as this cathedral-topped tree! Does a man bare his head in some old church? So did I, standing in the shadow of this regal tree, and looking up into that completed glory, at which three hundred years have been at work with noiseless fingers! What was I in its presence but a grasshopper? My heart said, "I may not call thee property, and that property mine! Thou belongest to the air. Thou art the child of summer. Thou art the mighty temple where birds praise God. Thou belongest to no man's hand, but to all men's eyes that do love beauty, and that have learned through beauty to behold God! Stand, then, in thine own beauty and grandeur! I shall be a lover and a protector, to keep drought from thy roots, and the axe from thy trunk."

For, remorseless men there are crawling yet upon the face of the earth, smitten blind and inwardly dead, whose only thought of a tree of ages is, that it is food for the axe and the saw! These are the wretches of whom the scripture speaks: "A man was famous according as he had lifted up axes upon the thick trees."

Thus famous, or rather infamous, was the last owner but one, before me, of this farm. Upon the crown of the hill, just where an artist would have planted them, had he wished to have them exactly in the right place, grew some two hundred stalwart and ancient maples, beeches, ashes and oaks, a narrow belt-like forest, forming a screen from the northern and western winds in winter, and a harp of endless music for the summer. The wretched owner of this farm, tempted of the devil, cut down the whole blessed band and brotherhood of trees, that he might fill his pocket with two pitiful dollars a cord for the wood! Well, his pocket was the best part of him. The iron furnaces have devoured my grove, and their huge stumps that stood like gravestones have been cleared away, that a grove may be planted in the same spot, for the next hundred years to nourish into the stature and glory of that which is gone.

In many other places I find the memorials of many noble trees slain; here a hemlock that carried up its eternal green a hundred feet into the winter air; there, a huge double-trunked chestnut, dear old grandfather of hundreds of children that have for generations clubbed its boughs, or shook its nut-laden top, and laughed and shouted as bushels of chestnuts rattled down. Now, the tree exists only in the form of loop-holed posts and weather-browned rails. I do hope the fellow got a sliver in his fingers every time he touched the hemlock plank, or let down the bars made of those chestnut rails!

BATS IN BURMESE CAVES

INTERESTING caves exist at Hpagat, twenty-six miles up the Salween, from Moulmein. They are hollowed out in the base of an isolated limestone hill about 250 feet high, rising precipitously from the river. Capt. A. R. S. Anderson, the surgeon-naturalist, gives an interesting account of these caves in an Indian government report which is abstracted by "Natural Science." The entrance is about twelve feet high and is much ornamented by Buddhistic sculptures. As the sun was setting the party took their stand on the sand-spit facing the entrance of the caves and soon saw a pair of falcons leave their perch on the trees and fly to and fro over the river. They were speedily joined by other birds, including common kites and jungle crows, and the entire flock, to the number of sixty or a hundred, flew to the entrance of the caves, close to which they remained wheeling about in mid-air. A few minutes later the bats began to issue in ones and twos, and were soon pursued by the birds of prey, but appeared to have no great difficulty in eluding capture by their rapid and jerky flight, and their pursuers made no very determined or long-sustained efforts to capture them, but soon returned to their vigil over the cave. A minute or two passed and a sudden rush of wings was heard, and the bats were seen to emerge from the cave in a dense stream which slowly became more and more packed, and continued of about the same density for some ten minutes and then gradually thinned away, until, at the end of twenty minutes, the last had emerged. The stream of bats when at its maximum was ten feet square, and so dense as to closely resemble smoke pouring from a chimney in a gale of wind. This resemblance was increased by the slightly sinuous course pursued by the bats as they flew off into the afterglow. They were so densely crowded that they frequently upset each other and fell helplessly into the river below, where they succeeded in reaching the bank only to fall a prey to the expectant crow. When the great rush occurred the falcons, kites, and crows entered the stream of bats and, flying along with it and in it, seized as many bats as they required for food. Capt. Anderson, by throwing his walking-stick into the stream of bats, obtained six specimens. During the last twenty years the bats appear to have considerably diminished in numbers, owing to the depredations of their bird enemies and to their constant disturbance by collectors of bat manure.

A METAL BIRD'S NEST

IN THE Museum of Natural History at Soleure, in Switzerland, there is said to be a bird's nest made entirely of steel. There are a number of clockmaking shops at Soleure, and in the yards of these shops there are often found lying disused or broken springs of clocks. One day a clock-maker noticed in a tree in his yard a bird's nest of peculiar appearance. Examining it he found that a pair of wag-tails had built a nest entirely of clock springs. It was more than four inches across and perfectly comfortable for the birds. After the feathered architects had reared their brood, the nest was taken to the museum, where it is preserved as a striking illustration of the skill of birds in turning their surroundings to advantage in building their nests.