. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 76 BOTANY. endosperm. If the student is a vefy careful observer, he may be able to make out the number of cotyledons in the young plant. There are fifteen seed leaves in one common species of pine. The number and position are better seen in a young seedling of three or four weeks' growth. The Uses of Seeds. — Some of the uses of seeds to man have already been noted. A seed is a very young plant usually provided with a store of food to give it a start in life. Its use to the parent plant is
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 76 BOTANY. endosperm. If the student is a vefy careful observer, he may be able to make out the number of cotyledons in the young plant. There are fifteen seed leaves in one common species of pine. The number and position are better seen in a young seedling of three or four weeks' growth. The Uses of Seeds. — Some of the uses of seeds to man have already been noted. A seed is a very young plant usually provided with a store of food to give it a start in life. Its use to the parent plant is incalculable, for it is by means of the seed that a plant reproduces its kind. This can be done, as we shall see later, to a limited degree by cuttings, grafting, and in other ways, but the usual way is by the produc- tion and planting of seeds. Not only does a seed serve to continue a species of plant in a cer- tain locality^ but it serves to give the plant a Pine seedling. foothold in uew places. Seeds may be blown by the wind or carried by animals, or by a hundred devices work their way to pastures new, there to establish outposts of their kind. Immense numbers of seeds may be produced by a single plant. This may be of great economic importance. A single pea plant may produce twenty pods, each containing from six to eight seeds. This would mean the possibility of nearly twenty-five thousand plants produced from the original parent by the end of the second season. A plant of Indian corn may produce over fifteen hundred grains of corn. On the other hand, many weeds produce seed in still greater numbers. A single milkweed may set free over two thousand seeds. A single capsule of Jimson weed has been found to hold over six hundred seeds. The thistle is even more prolific. Some seeds, especially those of weeds, are able to withstand great extremes of heat and cold and still to retain their ability to germinate. Some have been known to retain their vitality for over fifty years.
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