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Autumn Seeds
| Article
# : |
11670 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
9 / 1986 |
708 Words |
| Author
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Barbara Tufty
Barbara Tufty is a free-lance natural science writer
who lives in Washington, D.C. |
Autumn is a time of moving. As the northern hemisphere tips farther and farther away from the sun, shadows fall earlier and stretch longer across the great forests and fields of the north, and animals and humans start seeking warmer climates. Summer visitors close down their lakeside cabins; elk and deer move into the valleys as cold winds start to blow; geese and ducks trumpet through the night; bats zigzag toward warmer caves; and the monarch butterflies are on the wing to sunlit Mexico.
Some of the most amazing autumn wanderers are less recognized: the seeds of plants. Each seed is a remarkable package. Within its tough coat lies the vital, compact essence of genetic coding, meticulously stored to reproduce millions of their parents characteristics; height, form, shape, texture, and color - such as the scarlet-orange for poppies, milky juices for milkweed, dark green needles for pines, and scent for phloxes.
Incapable of moving on their own, seeds have evolved innumerable resourceful means for hitching rides on many vehicles - the wind, water, birds, animals, even humans.
Some seeds develop wings or lightweight appendages that catch the wind and lift the embryo into the air. The silver-white parachutes of dandelion seeds are familiar, as are the gossamer fibers of milkweed, thistle, goldenrod, and aster. Less spectacular seeds of the Compositae family of plants - coltsfoot, goatsbeard, salsify, and willow - have similar devices. Another kind of flying appendages are the wings on seeds of trumpet flowers and various trees, such as maples (though these seeds form in the spring), elm, ash, and ailanthus. Tumbleweeds, the rounded rolling bushes of the West, have contrived yet a third method of using the wind. When the seeds are nearly ripe, the whole plant breaks loose from the ground and tumbles wherever the wind blows. The seed capsules open gradually and scatter their contents as the bush rolls and shakes along the fields and plains. Tumble grasses act in similar fashion, as do ghost plants, white pigweeds, and Russian thistles.
Water is a carrier, too, conveying seeds of arrowhead or waterlilies that grow and nod over streams and ponds. A stiff stem holds the flower disk of the Egyptian or American lotus above the water while the seeds develop and dry in depressions in the flat upper face. When waves or wind shake the stalk, the seeds rattle out. With Asian lotus, the seed cup breaks off and turns upside down. As this strange boat drifts, the seeds drop out one by
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