. Fondements de la Botanique. La botanique. ROOTS 57. Fig. 26. - Un "Sprouting Bean poussant son Root-Tip Windsor en mercure. s, semence ; r, racine ; w, la couche d'eau ; m, mercure. à un bouchon de liège qui est attachée à l'abeille et de mélange de résine sur le côté d'un petit creux ou de panoramique en verre ou en terre cuite vernissée. L'huile est remplie d'une demi-pouce ou plus avec le mercure, et sur le dessus du mercure est une couche d'eau. L'ensemble est étroitement couvert par un grand gobelet ou une cloche de verre. Permettre à l'appareil de se tenir debout un- til la racine a forcé son chemin vers le bas dans le mercure. Exécutez ensuite une fine aiguille dans la racine où il

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. Foundations of Botany. Botany. ROOTS 57. Fig. 26. — A Sprouting "Windsor Bean pushing its Root-Tip into Mercury. s, seed ; r, root; w, layer of water ; m, mercury. to a cork that is fastened with beeswax and resin mixture to the side of a little trough or pan of glass or glazed earthenware. The pan is filled half an inch or more with mercury, and on top of the mercury is a layer of water. The whole is closely covered by a large tumbler or a bell-glass. Allow the apparatus to stand un- til the root has forced its way down into the mercury. Then run a slender needle into the root where it enters the mercury (to mark the exact level), withdraw the root, and measure the length of the part submerged in mercury. To see whether this part would have stayed under by virtue of its own weight, cut it off and lay it on the mercury. Push it under with a pair of steel forceps and then let go of it. What does it do ? 69. Discussion of Exp. XIX. — By comparing the weights of equal bulks of mercury and Windsor bean roots, it is found that the mercury is about fourteen times as heavy as the substance of the roots. Evidently, then, the sub- merged part of the root must have been held under by a force about fourteen times its own weight. Making fine equidistant cross-marks with ink along the upper and the lower surface"'of a root that is about to bend downward at the tip, readily shows that those of the upper series soon come to be farther apart, — in other words, that the root is forced to bend downward by the more rapid growth of its upper as compared with its under surface. 70. Geotropism. — The property which plants or their organs manifest, of assuming a definite direction with. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & co

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