Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 70 BOTANY Most of our trees, and vevy many of our common plants, belong to this great group of plants. How many of the parts inside the cotyledons can you identify and com- pare with similar structures in the bean? Look for hypocotyl, epicotyl, and true leaves. Are the structures named homologous with the same structures in the bean? How do 3'ou know? Draw the pea, showing all the above-named parts. Compare the pea seedling and bean
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 70 BOTANY Most of our trees, and vevy many of our common plants, belong to this great group of plants. How many of the parts inside the cotyledons can you identify and com- pare with similar structures in the bean? Look for hypocotyl, epicotyl, and true leaves. Are the structures named homologous with the same structures in the bean? How do 3'ou know? Draw the pea, showing all the above-named parts. Compare the pea seedling and bean seedling with regard to the following points: (1) as to the method of getting out of the ground; (2) as to the part which appears first; (3) as to the parts that ap- pear above ground; (4) the ultimate fate of each part. This must be made the subject of an extended home experiment. Drawings should be made to illus- trate each stage of growth, and each part should be carefully labeled.^ An experiment to prove the func- tion of the cotyledons of the pea may be made in very much the same way as the experiment per- formed to find out the same thing for the bean. This experiment can be made at home and brought in at the same time as the bean ex- periment, and comparisons made. Experiment to show the function of the coty- ledons of the pea, photographed at the end of two weeks. Note the size of the plants at the left, without cotyledons. Analogy. — A structure which has the same function or use as another structure is said to be analogous to it. Is the cotyledon of the pea analogous to the cotyledon of the bean ? Is it also ho- mologous? Cotyledons as Foliage Leaves. — In the young plants which we have just been talking about, the cotyledons hold a reserve food supply, but do not serve at any time as true leaves for the plant In many dicotyledons, however, the seed leaves do act as true leaves. This may well be seen in the squash seedling. Here the young plant has little or n
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