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Page:Popular Science Monthly Volume 18.djvu/528

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THE POPULAR SCIENCE MONTHLY.

the tips of eleven radicles within the same jars, and five of them became plainly curved away from this side. In the former case the bend was abrupt, as shown in Fig. 15; in the latter a greater length of radicle

PSM V18 D528 Pisum sativum.jpg
Fig. 16.—Pisum Sativum.—A radicle extended horizontally in damp air with a little square of card affixed to the lower side of its tip, causing it to bend upward in opposition to geotropism. The deflection of the radicle after twenty-one hours is shown at A, and of the same radicle after forty-five hours at B, now forming a loop.

seemed to be affected and the curve was symmetrical, as seen in Fig. 16. He says, "It was a striking spectacle, showing the difference in the sensitiveness of the radicle in different parts, to behold in the same

PSM V18 D528 Zea mays.jpg
Fig. 17.—Zea mays: Radicles excited to bend away from the little squares of card attached to one side of their tips.

jar one set of radicles curved away from the squares on their tips, and another set curved toward the squares attached a little higher up."

His experiments upon the radicles of dicotyledons were numerous and varied in every way; but the seeds of Indian corn were the only