. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 56 BOTANY dehiscent fruits the distinction between seed and fruit is always easy. In the indehiscent fruits it is not always so plain, espe- cially in the nuts, grains, and the achene fruits. In all of the above fruits it is necessary to remember that the pericarp, or ovary wall, adheres quite closely to the seed coat. In a grain of wheat the two have actually grown together. In a nut it is always possible to scrape off the seed coat, as a thin brownish covering around the kernel of the nut
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 56 BOTANY dehiscent fruits the distinction between seed and fruit is always easy. In the indehiscent fruits it is not always so plain, espe- cially in the nuts, grains, and the achene fruits. In all of the above fruits it is necessary to remember that the pericarp, or ovary wall, adheres quite closely to the seed coat. In a grain of wheat the two have actually grown together. In a nut it is always possible to scrape off the seed coat, as a thin brownish covering around the kernel of the nut. Try this with a chestnut. Homology of Parts in Flowers and Fruits. — In the acorn, chestnut, and hazelnut a number of leaflike structures come out on the branch just under the fruit and become the capsule of the acorn, the bur of the chestnut, and the husk of the hazelnut respectively. All these structures originate from the same place on the branch. Very early in their growth they appear to be leaflike. We have reason to believe that these structures are en- tirely similar to leaves in structure and position. Any part of a plant or animal that has the same position and structure as an- other similar part on another plant or animal is said to be homolo- gous with it. Homology of the Parts of a Flower. — It is believed by botanists that all parts of a flower (sepals, petals, stamens, and carpels) are homolo- gous to each other and also to leaves. It would not take a great stretch of the imagination for you to see how like leaves are the sepals and even the petals of some flowers. In roses and in the water lily the petals become thinner as we go inward and become tipped with yellow. On examination, this yellow tip is seen to be Horizontal diagram of a pollen box. In short, the petal has become a sta- a lily. The central . i • -^ ^ • i- ^ i i i. area represents the men. A very good imitation of a pea pod could be ovary; the bean made by folding a pea leaflet along the mi
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