. Essentials of biology presented in problems. Biology. 66 SEEDS AND SEEDLINGS with the micropyle in the seed. The thick outer coat (the testa) is easily removed from a soaked bean, the delicate coat under it easily escaping notice. The seed separates into two parts; these are called the cotyledons. If you pull apart the cotyledons very care- fully, you find certain other structures between them. The rod- like part is called the hypocotyl (meaning under the cotyledons). This will later form the root (and part of the stem) of the young bean plant. The first true leaves, very tiny structures, ar
. Essentials of biology presented in problems. Biology. 66 SEEDS AND SEEDLINGS with the micropyle in the seed. The thick outer coat (the testa) is easily removed from a soaked bean, the delicate coat under it easily escaping notice. The seed separates into two parts; these are called the cotyledons. If you pull apart the cotyledons very care- fully, you find certain other structures between them. The rod- like part is called the hypocotyl (meaning under the cotyledons). This will later form the root (and part of the stem) of the young bean plant. The first true leaves, very tiny structures, are folded together between the cotyledons. That part of the plant above the cotyledons is known as the plumule or epicotyl (meaning above the cotyledons). All the parts of the seed within the seed coats together form the embryo or young plant. A bean seed contains, then, a tiny plant tucked away between the cotyledons arid pro- tected by a tough coat. 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 ani- mals get in the egg) from food provided for it within its own body. Test for Starch. — If we shake up a piece of laundry starch in water, in a test tube, and then add to the mixture two or three drops of iodine solution,^ we find that the particles of starch in the test tube turn pur- ple or deep blue. It has been discovered by experiment that starch, and no other knoivn Starch grainsTXe cells «"^«^«^ce, Will be turned purple or dark blue, of a potato tuber. Therefore, iodine solution has come to be used as a tes
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
