Plants and their ways in South Africa . Growth of Roots, Stems, and Leaves 21 more apparent by thrusting into the soil two slender wire rods, one oneither side of the stem. Growth Curvature affected by Water.—We havebeen studying growth curvatures affected by gravity. Whilethe tendency of the main root is downward and that of the. Fig. 29.—Leaves of young castor-oil plant looking toward the light. Stem is upward, both are sensitive to other influences. Foodmaterial which roots absorb must be dissolved in water, insearch of which they often go a long distance. The roots ofa tree growing by a st
Plants and their ways in South Africa . Growth of Roots, Stems, and Leaves 21 more apparent by thrusting into the soil two slender wire rods, one oneither side of the stem. Growth Curvature affected by Water.—We havebeen studying growth curvatures affected by gravity. Whilethe tendency of the main root is downward and that of the. Fig. 29.—Leaves of young castor-oil plant looking toward the light. Stem is upward, both are sensitive to other influences. Foodmaterial which roots absorb must be dissolved in water, insearch of which they often go a long distance. The roots ofa tree growing by a stream will reach far out on the sidetoward the water, Young plants show this curvature. 22 Plants and their Ways in South Africa Ex. 7. Cover the outside of the glass germinator or of a funnel withseveral thicknesses of flannel. Fasten seeds which have just germinatedby means of a narrow strip of flannel to the upper edge of the the flannel moist, and the roots will follow the inclined face of thegerminator instead of growing vertically. The flannel must not be toomoist, or the roots will turn from it. Ex. 8. Growth Curvatures caused by Light.—Place the germinatorin a box lighted at one end. Notice the seedlings in a day or so. Thestems will bend towards the lighted end. Will the roots show a turningaway from
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1915
