wild bean and similar plants produce a great many seeds in a seed pod. This holds the seeds until they are large FIG. 237. Five different devices for the scattering of seeds. Do you know the plant that produces each? long distances. Seeds are also and ripe. Then the pod becomes so stretched that it bursts, and the seeds fly out through the air, and fall some distance from the parent plant. Some plant seeds, such as those of the dandelion, maple, and thistle, have downy structures, like umbrellas with little wings. The wind catches these seeds up, and carries them for comparatively carried far away by water. The ocean itself carries seeds from one land to another. Another device for scattering seed is seen in the cocklebur and burdock. The plants surround their seeds with stickers, which catch on the fur of animals, including the clothing of boys and girls, and are thus carried to new fields to grow. We owe the benefits and pleasures derived from many fruits to the efforts of the plants to scatter their seeds. The fleshy part of the fruit which we eat is simply a ripened part of some of the reproductive organs of the plant. The fruit is carried away by man and animals. The fleshy part is eaten, and the seeds grow where they are thrown, in a new location far from the parent plant. Of course man has greatly developed many fruits to improve the form which nature gave them (see § 334). On the 309. What are the Lower Plants Like? north side of tree trunks and on old fences, you have often noticed a green stain. This is one of the simplest of plants; it is called pleurococcus (plū'rō-kõk'ŭs). Each plant is so small that it has to be magnified by a microscope to be seen at all. Indeed, each plant consists of only one cell (see § 296). This plant does not produce seeds, but simply splits, or divides, to form two or more plants instead of one. The new cells each contain part of the original cell, and grow to full size. Between the pleurococcus and the flowering plants, there are many groups of plants. One of these groups is called the fungi (fŭn'jī; the singular is fun'gus). These are such plants as toadstools, mushrooms, Tetanus and puffballs, which do not produce Milk Bacilli Bubonic P. Micrococci Asiatic C. Typhoid F. 0 Typhus F. Pond Spirilla FIG. 238. - Some kinds of the tiny plants we call bacteria, bacilli, and micrococci, all highly magnified. Bacteria (see Fig. 238) are also a low order of plants. They have only one cell. They are reproduced very rapidly by division of cells, as the pleurococcus is. Certain bacteria (see § 204) cause milk to sour; certain others make meat decay; others still cause some of the different diseases which are common to plants and animals. Mosses and ferns do not produce flowers, or true seeds either. Ferns are cultivated by gardeners for their beautiful fronds, or leaves. Fir trees, pines, and hemlocks belong to the cone-bearing plants. The stamens and pistils of the flowers are produced in cones, and the seed is not inclosed in a special seed case as in the flowering plants (see Fig. 239). FIG. 239. On the left, the young cone of a spruce; on the right, the old cone of a pine. The seeds are thrown out when the dried "scales" open. Have you ever seen the palegreen, strange-looking new cones of the fir or pine in the springtime or early summer, or the dried, little, brown cones of some Christmas trees? 310. Are Wild Flowers Worth Preserving? - When the early settlers came to America, they found a land filled with wild plants and animals, and only a few people, the Indians, to use them. So they killed the animals, and destroyed the trees and other plants as they wished; for they felt that there were so many of every kind that they could not possibly use them up. But Americans have learned long since that some of our native animals will be entirely gone, or " become extinct," if they are not protected. So laws have been made to prevent the killing of deer, wild ducks, and other game, except at certain seasons, and then only in certain amounts. The same is true of certain kinds of fish. The buffalo is an animal which once roamed our prairies in numbers, but became almost entirely extinct. Now the government does not allow the buffalo to be hunted. Why is this done? Perhaps the deepest reason for the preservation of the buffalo in this country is that this animal is a wonderful form of life, which formed a part of original America; hence some of these animals ought to be left, in order that Americans of the future may still be able to enjoy seeing them. How about the wild flowers of our country? Did you know that some kinds of our native plants have been almost entirely destroyed by thoughtless people? Is it not worth while for us to think of our wild plants, as of our wild animals, as a part of original America, and to see to it that they are not utterly destroyed? Do you not think that you can get far more pleasure from wild plants if you let them grow, so that you can go back to see them from year to year, than from tearing them up to wither and die? Few wild flowers will last long when carried from the country to the city. Certainly, even country children ought to be content to pick only a few flowers of any one kind, and to leave the others to grow for the enjoyment of themselves and their fellow Americans in future years. 311. Exercises. 1. Name some plants and trees of the desert portions of the United States. What is peculiar about them? 2. How is a celery stalk made white? Why? What is the color of a potato sprout in a dark room? What is the color of grass that grows for a time under a board, or under a pile of leaves? What happens when such grass is brought into sunlight? 3. Have leaves a form which makes it possible for them to shed water? 4. Are young plants ever started from any structures except the seed? How are potatoes planted? What is meant by the "slipping" of such plants as geraniums? Is the strawberry developed from its seeds? 5. What leaves are of importance as commercial products? 6. What is the difference between the embryo plant and the seedling? 7. How does the tumbleweed scatter its seeds? 8. Examine some buds and tell the different ways in which they are protected from cold weather. 9. Describe the stems of the cherry, oak, maple, catalpa, cottonwood, hickory, and linden (boxwood) trees. Describe their leaves. Describe their fruit. 10. Describe the flower of a dandelion. Is it one flower, or many? What is each separate flower like? Summary. Plants need food for energy and for growth and repair. Unlike animals, green plants can build up their food directly from materials in the soil and air. The organs of a plant are root, stem, leaves, flower, and seeds. The two necessary plant duties are nutrition and reproduction. A seed consists of the embryo, or germ, and the food stored for its use. Germination, or sprouting, is the process by which the embryo becomes an independent plant. Leaves have a blade, usually a petiole, and sometimes stipules. They may be parallel-veined, feather-veined, or palm-veined. They may also be simple or compound. A leaf is covered with a colorless epidermis containing breathing pores, or stomata, through which the interior of the leaf communicates with the outer air. In sunlight the leaf, because of its chlorophyll, is able to convert carbon dioxide and water into carbohydrates and oxygen. Plants climb by means of twining stems, tendrils, and flat disks. Stems usually produce buds and branches in the axils of leaves. Stems may also grow underground, as rootstocks. |