Wednesday, July 30, 2008

Travels of Seeds



Some Are Fitted With Parachutes, Which Carry Them — The Dying Mother "Rose of Jericho" — How Seeds Are Distributed by Animals and Water.

Nature has spared no pains to provide for the perpetuation of living organisms. She is prodigal, even apparently wasteful, in her efforts to attain this end. Every plant throws out yearly its myriads of seeds, and no small part of the machinery adapted to make this product fulfill its mission is that directed to the distribution of these seeds. So effective is this machinery that plants spread in a few years over wide regions. Witness the incursions of weeds like the so called Russian thistle, against which the efforts of the farmer seem almost unavailing. The means by which this rapid spreading is brought about are the subject of an article by Professor F. Muller in "Der Stein der Weisen," Vienna, of which we translate the most interesting portions:

"Who has sent them (the plants) as colonists into this new, unpeopled land? Whence have they come and by what way? If we call the roll of the army of colonists that we may get an answer to this question, we shall find especially plants whose seeds can navigate the air like miniature flying machines, often for long distances. All these belong to the widely distributed aster family (compositæ) or to the nearly related teazel family (dipsaceæ). Their seeds are furnished, to fit them for their long sails through the airy sea, with a sort of parachute of soft, feathery fibers. The lightest breeze raises them and bears them in graceful sweep over field and meadow, but the storm wind lifts them to the region of the clouds so that they fly with the eagle over hill and dale to far and foreign lands. Millions, to be sure, fall to the ground without reaching the sought for soil, but other millions fulfill the end of their existence, the perpetuation and increase of their kind. Next to the composite plants is the numerous mustard family (cruciferæ). Then comes the pink family with its countless representatives and the plain looking grass family, whose light seeds fly about hither and thither as the stems are tossed about by the wind.

"When a summer thunderstorm bursts, bending the strongest trees, or when in autumn the wind rushes through the woods, then the time has come when the plant children, now only slightly attached to the plant mother — that is, the ripe seeds that cling to them — are torn away and set out on their adventurous travels; then they whirl and dance in the air, along with thousands on thousands of their fellows. Many rise high in air and sail on the upper air currents far away; others remain in the tree tops or hang from the branches; others still fall on roofs or bare rocks; many, too, drop on passing men or beasts. Chance bears few to a place where their growth is assured. The greater part must perish."

After mentioning the various trees that have winged seeds, such as the ash, maple, etc. Professor Muller goes on to describe a peculiarly interesting plant belonging to this class — the "rose of Jericho." He says:

"The spherical plant, resembling a bird's nest in the foreground, is the so called 'rose of Jericho' (Anastatica hierochuntia), belonging to the family of cruciferæ. When the plant approaches maturity, it forms by the bending of its branches a spherical ball that carries the fruit within. Now the dying mother plant is ready for its journey over the desert. When, with the help of the wind, it has become detached from the ground, it is rolled about in the storm, hopping and springing over the earth, now leaping over some rock that protrudes from the sea of sand, now over the bleaching skeleton of some unlucky wanderer of the desert, all the time strewing its seeds far and wide.

"There are also many plants whose seeds, by means of mechanical devices, are hurled forth from the plant, as in the oxalis family, the geranium and many others. Such seeds, however, can travel only short distances, and that is the reason why we almost never see the plants growing singly, but in groups together. Still sometimes they are carried to great distances by passing animals, and also by flowing water.

"There is a large number of plants whose seeds are carried in the stomachs of animals and so make long journeys. Water also plays a great part in the distribution of plants, and in the case of newly formed islands it plays the principal part.

"Who has not on an autumn walk through wood and field brought home those little hangers on, clinging to his clothes, or been obliged angrily to free himself from the troublesome obstructions while still on the road? Unwittingly he has thus aided in the distribution of these plants, and, equally unwittingly, animals carry the seeds in their fur and birds bear them on their feathers, whence they are sooner or later dislodged. The skill shown by nature in the matter is truly remarkable. Those plants are mostly troublesome weeds which one would rather see decay and perish, but nature makes use of us against our wills to serve for their propagation. We are like that strict professor who, to see that there should be no cheating in a written examination, went about from scholar to scholar and thereby unwittingly aided them to cheat, for he carried about with him a placard bearing the answers to all the questions, which some sly scapegrace had pinned to his coattails.

"In this connection the interesting fact should be stated that very many plants whose fruits serve to nourish neither man nor beast have those devices for securing the distribution of their seeds. In the case of plants whose fruits are sought as food this very fact is sufficient security that the seeds will be properly distributed." — Literary Digest.

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