. Cyclopedia of farm crops. Farm produce; Agriculture. THE PLANT: ITS STRUCTURE, LIFE - PROCESSES AND ENVIRONMENT 15 contained in the water. The leaf thus becomes the meeting place of air food and soil food. These two sorts of crude food combine to form elaborated food. The first step is probably the formation cf sugar, which then, by combining with nitrogen, sulfur, phosphorus and other elements, forms pro- teids. These move from place to place, principally in the bast, and so reach the regions where they are needed. The energy needed to elaborate food comes from the sunlight. The leaves have
. Cyclopedia of farm crops. Farm produce; Agriculture. THE PLANT: ITS STRUCTURE, LIFE - PROCESSES AND ENVIRONMENT 15 contained in the water. The leaf thus becomes the meeting place of air food and soil food. These two sorts of crude food combine to form elaborated food. The first step is probably the formation cf sugar, which then, by combining with nitrogen, sulfur, phosphorus and other elements, forms pro- teids. These move from place to place, principally in the bast, and so reach the regions where they are needed. The energy needed to elaborate food comes from the sunlight. The leaves have various devices to absorb all the sunlight possible. Some " follow the sun" all day long, thus facing eastward in the morning and westward at evening. At mid-day they are horizontal, except when the sunlight is exces- sive, in which case they assume the " profile posi- tion" with the edges pointing upward, thus avoid- ing injury due to too strong light. Many such leaves assume a "sleep position" at night by fold- ing ; they diminish thereby the loss of heat and avoid the precipitation of dew on the protected surfaces. Most leaves have the power of turning toward the light, and so move out of the shadow of other leaves. Thus arise the beautiful " leaf-mosaics," e. g., of English ivy or of maple, in which no leaf unduly shades another. The usual arrangement of leaves on the stem is in regular vertical rows. The arrangement is known as phyllotaxy. The stem.âThe stem bears the leaves and fur- nishes them with a constant supply of water, which it conveys from the root. On placing a plant with its roots in diluted red ink or other colored solution, we can trace the colored solution up through the wood-cells in the root (Fig. 29), through the stem (Fig. 36), into the finest veins of the leaf. It is easily seen that the colored solution travels only in the wood-cells and not in the other cells of the stem. We usually find the wood-cells associa
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectagriculture, bookyear
