. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. SEEDS AND SEEDLINGS 67 true leaves folded together between the cotyledons. How many leaves are there ? That part of the plant above the cotyledons is known as the -plumule or epicotyl (meaning above the cotyledons). Later we shall wish to know what part of the future plant the epicotyl forms. All the parts of the seed within the seed coats together form the embryo or young plant. Draw the bean to show all the above parts, twice natural size. Label every part carefully. Food in the Cotyledon
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. SEEDS AND SEEDLINGS 67 true leaves folded together between the cotyledons. How many leaves are there ? That part of the plant above the cotyledons is known as the -plumule or epicotyl (meaning above the cotyledons). Later we shall wish to know what part of the future plant the epicotyl forms. All the parts of the seed within the seed coats together form the embryo or young plant. Draw the bean to show all the above parts, twice natural size. Label every part carefully. Food in the Cotyledons. — The problem now before us is to find out how the embryo of the bean is adapted to grow into an adult plant. Up to this stage of its existence it has had the advantage of food and protection from the parent plant. Now it must begin the battle of life alone. We shall find in all our work with plants and animals that the problem of food supply is always the most important problem to be solved by the growing organism. Let us see if the embryo is able to get a start in life (which many animals get in the egg) from food provided for it within its own body. Experiment. — Mash up a little piece of a bean cotyledon which you have previously soaked in water. Test for starch with iodine solution What color appears? If you now mount a little of the stained material in water on a glass slide under the compound microscope, you will find that the starch is contained in the form of little ovoid bodies called starch grains. The starch grains and other food products are made use of by the growing plant in a manner which we shall later know more about. Test the cotyledon of a bean, for proteid food, with nitric acid and ammonium hydrate. The change of the color of the surface shows us that considerable proteid is present. According to the compilations from the government reports, the kidney bean is one of the materials very rich in proteid food. It con- Starch grains in the cells tains n
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