Plants and their ways in South Africa . riment we haveseen that the tip is the part which is sensitive to this stimulus. It is calledthe perceptive zone. Ex. 6. The Direction of the Stem.—The stem has as strong an up-ward growth as the root has a downward tendency. Place seedlings thathave grown in pots or in the germinator in a horizontal position. Inthree or four hours a decided change of direction has taken place. InFig. 28 notice that the one at a is curving, although the end was the stem curvatures of monocotyledons. Where does curvaturetake place in the jointed stems of grass
Plants and their ways in South Africa . riment we haveseen that the tip is the part which is sensitive to this stimulus. It is calledthe perceptive zone. Ex. 6. The Direction of the Stem.—The stem has as strong an up-ward growth as the root has a downward tendency. Place seedlings thathave grown in pots or in the germinator in a horizontal position. Inthree or four hours a decided change of direction has taken place. InFig. 28 notice that the one at a is curving, although the end was the stem curvatures of monocotyledons. Where does curvaturetake place in the jointed stems of grasses ? In Commelina ? After the seedlings have become upright, turn the pot hall-way how soon a change of direction may be observed. It will be made 1 The roots are injured by the shock, but an experiment which may beperformed to show this without injury requires an elaborate piece of ap-paratus. If care is taken, the tip may be slit lengthwise. In spite of theinjury the root will still bend down as the root is not 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
Size: 1391px × 1797px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1915
