Page:Popular Science Monthly Volume 38.djvu/50

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THE POPULAR SCIENCE MONTHLY.

and an added significance is given to the following words of Darwin, with which he closes his memorable work: "We believe that there is no structure in plants more wonderful, as far as its functions are concerned, than the tip of the radicle. If the tip be lightly pressed, or burnt or cut, it transmits an influence to the upper adjoining part, causing it to bend away from the affected side; and, what is more surprising, the tip can distinguish between a slightly harder and softer object, by which it is simultaneously pressed on opposite sides. If, however, the radicle is pressed by a similar object a little above the tip, the pressed part does not transmit any influence to the more distant parts, but bends abruptly toward the object. If the tip perceives the air to be moister on one side than on the other, it likewise transmits an influence to the upper adjoining part, which bends toward the source of moisture. When the tip is excited by light, . . . the adjoining part bends from the light; but when excited by gravitation, the same part bends toward the center of gravity. In almost every case we can clearly perceive the final purpose or advantage of the several movements. Two, or perhaps more, of the exciting causes often act simultaneously on the tip, and the one conquers the other, no doubt in accordance with its importance for the life of the plant. The course pursued by the radicle in penetrating the ground must be determined by the tip; hence it has acquired such diverse kinds of sensitiveness. It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals; the brain being seated within the anterior end of the body, receiving impressions from the sense-organs, and directing the several movements."


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MY CLASS IN GEOMETRY.

By GEORGE ILES.

A VIVID recollection of my boyhood is the general disfavor with which my school-fellows used to open Euclid. It was in vain the teacher said that geometry underlies not only architecture and engineering, but navigation and astronomy. As we never had any illustration of this alleged underlying to make the fact stick in our minds, but were strictly kept to theorem and problem, Euclid remained for most of us the driest and dreariest lesson of the day. This was not the case with me, for geometry happened to be my favorite study, and the easy triumph of leading the class in it was mine. As years of active life succeeded my school-days I could not help observing a good many examples of the