« ΠροηγούμενηΣυνέχεια »
Roots hold plants firmly in the soil and absorb the plant's food from the soil.
Flowers are the reproductive organs of the higher plants. When complete they consist of sepals, petals, stamens, and pistil.
The union of pollen from the stamens with an ovum of the pistil is called fertilization. It often depends upon birds and insects.
Many plants have special devices for scattering their seeds.
Only the higher plants produce seeds in a closed seed case. such plants as firs, pines, and hemlocks the seeds are produced in
Wild flowers, like wild animals, are worth preserving for future generations.
PLANTS OF USE TO MAN
312. How Does Man Make Use of Plants ? — We have learned something of the work of plants in nature and that they furnish food for animals and man, and much of the shelter and clothing of man. Do plants do this“ on purpose, or because, as they carry on their own life, work, they prepare materials which man wants and uses ? Thus the bean plant stores the cotyledons of its seed with food for the young plant (see § 298); but man eats the seed to nourish himself. So trees grow strong trunks to lift their leaves high into the sunlight and to stand firmly against the wind; but man uses the tree trunks for telegraph poles and boards. In the same way the maple tree has in early spring a sugary sap intended for the nourishment of the new growth of the tree; but man drills holes into the trunk, and secures a juice which he “boils down ” to form maple syrup and maple sugar. . Can you name some other cases of the same sort?
Fortunately for man, he has been able to find in almost every land the plants he needs for his life, and in the days in which it was hard for him to travel from one region to another he could make use of what he found in his own neighborhood. Nowadays many plant products which were unknown to our forefathers, or only luxuries, are common articles of food or clothing, because of the rapid transportation made possible by steamships and railroads. What are some foods that come from far-away lands? When these lines of transportation fail, as they did in the Great War, even a highly civilized country may find itself suffering, and in danger of starvation, because of the lack of some articles it has come to depend upon for food.
Man has brought in not only the products of the plants of other lands, but he has brought in the plants themselves, and tried to grow them. In some cases he has not succeeded; but in many others he has been able to grow the plant as well in its new home as in the old. So we have in our own country some common food plants that are native to America, and others which were either brought in by the early settlers, or recently introduced by expert growers. Thus, most of our California oranges come from plants originally brought from Brazil; while our cultivated strawberry plants are probably descendants of some that came from Chili. Indian corn, tomatoes, and potatoes are native American plants which have been carried to other parts of the world since the discovery of America. Can you name any others?
313. Does Man Eat Grass ? — Do you think it is
? ridiculous for us to speak of man's eating grass? It will not seem so when you learn that not only the grass of our lawns and of country meadows, but our common grains, such as wheat, corn, and rice, are really members of the same family, or group; this is called the grass family. The grass family of plants is made up of thousands of kinds. These are very different in size and in some other qualities, but they are alike in having very simple flowers and in producing a fruit which is seedlike. The flowers grow in close clusters. You would
. not think them flowers at all, perhaps, for they have only the stamens and the pistils, and neither sepals nor petals. Have they the really necessary organs? From the fact that the flowers of the grass family are not showy, would
you think that they need the help of insects to get the pollen from the stamens to the pistils? Why?
The grasses have peculiar little scales, or bracts, which serve as a protection for the seed, or grain. It is these bracts that fly off and fill the air of the farm granary at threshing time. We call it chaff. Have you ever seen the process of threshing wheat, by which the grain is separated from the stalk and chaff, and is made ready for the mill?
Can you find some grass which has “ seed,” or some dried stalks of timothy hay? If possible, get some unthreshed wheat, or stalks of oats of last year, and examine its stem and leaves and the dried bracts and grain upon it.
Soak a grain of corn in lukewarm water, and ANT
then remove its outer covering. Do you get any evidence of two “halves," as in the case of the
bean? No, the corn and all the other grasses Fig. 240. — A stalk of Indian corn,
have only one cotyledon in the seed, instead of with its tassels (at two. the top) and ears (on the sides). Note
Corn (Fig. 240) is different from the the silk projecting from the tops of the other common grasses in the way its
organs of reproduction are arranged. It has only the stamens and pistils of the flower, as is the case with the others, but these organs grow some dis
tance apart. The stamens are the “ tassels,” and grow in clusters at the tips of the stalks; the pistils grow in the axils of the leaves (see § 303) on the sides of the stalks. The pistils are protected by large bracts. Where do we find the ears of corn? Are the ears developed stamens or pistils ? What is the “silk” which projects from the tip of the ear?
314. What Grasses Does Man Use? — We have already learned that wheat, corn, and rice belong to the grass family; the same is true of oats, rye, barley, and millet. We must not forget some grasses which are not used for their seed, but for their juice, or sap; these are sugar cane and sorghum. There is also the important grass that grows to the size of a tree, the bamboo. Where does the bamboo grow? Neither must we forget the grasses we dry and use for fodder for the animals of the farm in winter. The most important of these are timothy and redtop. There is also blue grass, so called from its blue-green color, which forms the wonderful pasture grass of Kentucky and the neighboring states and makes such excellent grass for the lawn.
Wheat is grown chiefly in the Northern States, although some kinds of it do well in regions of limited rainfall, such as are found in parts of Texas and Oklahoma. It does not do well in the moist, cold climate of northern Europe, but grows wonderfully in parts of Russia. A large crop comes from Argentina. There are two kinds of wheat, according to the time they are planted. One is called winter wheat, and the other spring wheat. How can wheat planted in October be kept from freezing ?