Although plants have no legs they are not devoid of mobility. When man uses the propulsive power of steam to travel by, he shows no greater ingenuity than do plants in their use of special devices of locomotion.
Species like the Tumble Weed (Amarantus Albus) pull up stakes, and, consigning themselves to the swift autumn winds, race across country at great speed, scattering seeds as they go. The Utriculariae or Bladderworts are true sailors and float about on inland streams like little ships. The Duckweeds and Wolffias also have aquatic habits.
However, most plants prefer to travel in embryo. In the form of small and microscopic seeds the force of gravity has little influence on them, and they can journey for long and incredible distances.
To this end practically every seed in existence is provided with some apparatus or appendage designed to help it make its way in the world. The Elm, the Linden, and the Ash bear winged seeds, which are so efficient in riding the breeze that they are really miniature aeroplanes. The double wings of the Maple are very much like those of an insect. The seeds are released from their container in such manner as to acquire a whirling motion as they fall.
The progeny of the Willow is provided with long projecting hairs which curl together to form a tiny balloon. Feathery attachments called pappus enable the children of the Dandelion, the Thistle and the Fire Weed to go on long jaunts of exploration.
The seed-pods of the Sycamore are great rollers. Even ordinary nuts and fruits may be blown to considerable distances by the strong winds of autumn. The many edible seeds and fruits are carried gratis by birds and animals. The Mistletoe, for instance, is distributed entirely by them.
Walnuts, Butternuts, and Acorns bear water travel well, as do certain of the hard seeds. The Arrowhead (Sagittaria) has a self-made water-wing on which its offspring float.
Plant seeds, which like to travel on animals, all provide themselves with grappling irons in the shape of sharp hooks, spurs and spines with which they cling to their carriers. Everybody in the northern United States knows of the avidity with which the Cockle-bur clings to any passing object. The Touch-me-not (Impatiens), the Wistaria, and a host of others, actually shoot their seeds from their pods as from a gun.
Every vagrant breeze, every purling brook, every deep river, every ocean current, is a highway of travel in plantdom. The birds, the beasts, the insects, and not least, man himself, are involuntary vehicles on which our vegetable friends tour the world. The spores of Mosses, Lichens, Fungi and other cryptogams are so light that they find no difficulty in mounting into the air and traveling across the Atlantic or Pacific Oceans at will.
The complete record of plant conquests would fill many volumes. Their operations have extended into every land and have had influence on the world’s history. It very often happens that plant invaders become so quickly and thoroughly naturalized in a strange country that they go a long way toward supplanting the original inhabitants in a very short time.