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One thing the foresters had to learn by experience in selecting the groups to be left for "mother-trees" was that they should be on the ridges and higher points of land where they are most exposed to the winds, so that the seeds will be carried as far as possible. And yet I suppose practically all of us know perfectly well that seeds fly "on the wings of the wind," to use the grand, poetic phrase of the Bible; which only goes to show again that we may have valuable information in our heads and yet fail to put it to use at first, when some occasion requires it. The Linden has a regular flying-machine, a monoplane, and one that carries several passengers at a time. In ordinary winds the wings of seeds don't keep them long afloat; and even in a fairly strong breeze, they seldom travel more than two or three times the height of the tree. I'm speaking of such seeds as those of the Maple and the Linden. The little Pine-seeds are carried much farther. And the tufts on the seeds of the Pussy-Willows and their kin, while they aren't what a bird would call wings at all, I suppose, keep them afloat in a wind of only two miles an hour. And some of these winged seeds have flying tricks that help. A Pine-seed, for example, carries its little wing in such a position that the seed whirls as it falls, and so it descends very slowly. See the advantage of that? This increases its chances of catching any outbound trains among passing wind currents. It may thus be able to take long journeys simply by "changing cars" from time to time. A horizontal puff may carry it out and away from the parent tree; then another, an upbound current, may carry it to where there are stronger breezes and where its movements are less likely to be interfered with by other trees. In very strong winds not only Pines but other winged seeds may be carried several miles. This explains why you find trees like the Gray Birch and the White Pine growing in the middle of pastures, far away from the woods. HOW THE PINE-SEEDS PUT ON THEIR WINGS Because the Pine-seeds are such clever travellers and can, in their different species, accommodate themselves to so many varieties of soil and climate, you find them everywhere -- on barren wastes, on the edges of rivers and lakes, or climbing the mountains to the timber-line, or clear on the borders of salt water, where no other tree dare go, bravely facing the fierce winds from the sea. The cones mature the second or third year after flowering. The seeds are in pairs, attached at the base, in shallow depressions, to the inner surface of the scales. As they fall from the cone they take with them the thin lining of the cone scales, and these are their wings. Yet they are delicate little bodies, these seeds, and must not be allowed to become too dry or they won't grow. QUEER HOOP-CHASING BY THE WIND SPRITES But the seeds of a tree don't necessarily have to have wings in order to be helped along by the wind. Even the Oaks, and nut-bearing trees like the Hickory, get a lift now and then in a threshing gale, but the Locust has a special device. Haven't you noticed how its big "pea-pods" -- it belongs to the pea family, by the way -- in drying, contract and so become twisted and curled? And then did you ever see them go rolling before a stiff breeze? It's a queer sort of hoop-chasing on the part of the wind sprites; but what these wind sprites are really doing, from a practical standpoint, is distributing the seeds of the Locust. THE WINDS AS SEED-GROWERS The concerns that raise seeds in their big gardens we call seed-growers, although all they do is to plant seeds already made by Nature and leave Nature to multiply them. Certainly, then, we can call the winds "seed-growers," can't we, when they actually help to make the seeds, just as much as a shoemaker makes shoes when he puts the soles and the uppers together? All seeds that come from wind-pollinated flowers are, in this sense, "made by the winds." Such flowers, having no direct means of communication with other flowers by the famous Bee Line, and similar routes, are obliged to produce their pollen grains in enormous quantities. Near Pine woods, in the season, you'll find sheets of water covered with the yellow dust; and you know, when you bring home a Pussy-Willow or the catkins of an Elm or an Ash, how thick the pollen settles around the vases in which they are put. The pollen grains of wind-borne seeds are smooth, not rough, as are those of insect-pollinated flowers. This roughening is to make the grains stick to the bees and other visitors and to each other, so the little carriers will be well loaded; but the smooth grains of the wind-borne pollen don't stick to one another and thus are enabled to float longer in the air and be carried farther. Moreover, the pollen grains of the Pine have two little balloons, called "flotation bladders," at opposite ends of the grain. These remarkable "dirigibles" have been known to travel over 500 miles! SCATTERING TREE SEEDS BY BOWS AND ARROWS So you see the winged seeds not only anticipated our air-planes but our dirigibles also! Very picturesque is the method employed by the city fathers of Seattle to build up a better watershed near the source of the Cedar River from which Seattle gets its water-supply. Men plant the tree seeds along the barren, rocky walls of that region by fastening little bags of the seed to the heads of arrows and then shooting them against the walls. This bursts the bags, and many of the seeds, caught in the cracks and crevices of the rocks, later reappear as brave little Cedars, Firs, and Hemlocks. What these bows and arrows do, the winds are constantly doing. That's why you see trees of the Pine family clinging to rocks so steep and high that it would almost make a fly dizzy to climb them! |
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