. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 24 BOTANY Functions of the Parts of a Plant. — Still more prominent are the structures we call flowers and fruits. Each of these structures differs from each other part, and each has a different work or function to perform for the plant. The root holds the plant firmly in the ground and takes in water; the stem holds the leaves up to the light; the leaves, under certain conditions, manufacture food for the plant; the flowers form the fruits; the fruits hold the seeds, which in turn reproduc
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. 24 BOTANY Functions of the Parts of a Plant. — Still more prominent are the structures we call flowers and fruits. Each of these structures differs from each other part, and each has a different work or function to perform for the plant. The root holds the plant firmly in the ground and takes in water; the stem holds the leaves up to the light; the leaves, under certain conditions, manufacture food for the plant; the flowers form the fruits; the fruits hold the seeds, which in turn reproduce young plants of the same kind. Organs.— Each part of a plant or animal, having a separate work or function,is known as an organ. Most plants and animals are composed of organs; hence any hving thing, even the simplest single living cell, has come to be called an organism. If we look rather carefully from all sides at the organ called the leaf, we find that the materials of which it is composed do not ap- pear to be everywhere the same. The leaf is much thinner and more delicate in some parts than in others. Holding the flat, expanded blade to the branch is a little stalk, the petiole, which extends into the blade of the leaf as a se- ries of little veins which evidently form a framework for the flat blade somewhat as the sticks of a kite hold the paper in place. In the same manner the veins, if cut crosswise and mounted on a glass slide under the compound microscope,^ show that they are made up of building material which, although microscopic in size, yet differs considerably from other material in the same part of the vein. The smallest units of building materia] of the plant or ani- mal disclosed by the compound microscope are called cells. The organs of a plant or animal are built of these tiny structures. Tissues. — The cells which form certain parts of the veins, the flat blade, or other portions of the plant, are often found in groups * For a study of the compound
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