Page:Popular Science Monthly Volume 90.djvu/693

 Popular Science Monthly

��677

���In the center is a tendril showing the windings in two directions and the hook in the center. At sides the principle is illustrated with a strip of paper over a pencil

��Why the Tendrils of a Plant Grow in Two Directions

WHEN a climbing plant has attained such a height that. its weight will prevent it from growing upward it begins to throw out tendrils which grasp other bodies for the purpose of support.

Somehow the plant knows where a neighboring object is to be found and throws out tendrils in that direction. At first the tendril is straight, but as the object to be grasped is approached a little hook is formed to act as a catch. The moment this has been accomplished the tendril begins to coil up, going first from right to left, then forming a loop and going from left to right.

Such a tendril is so elastic that there is little danger of its snapping off when the vine is subjected the sudden strain imposed b) the alighting of a bird or the blowing of a sudden gust of wind.

But why should the tendril grow in two directions? This is a question which has puzzled many. It is answered in the illus- tration above.

In the center of the illustration is a photo- graph of a tendril, showing the two coils in opposite directions and the loop between them. Now let us take a narrow paper ribbon and coil this around a pencil as at the

��left of the illustration, meanwhile holding the unwrapped portion firmly between the fin- gers. For ever>- turn we make around the pencil, the other portion of the ribbon will make a corresponding twist. If we were to continue the process the twist would finally become so tight that the paper would tear. If we make a loop in the ribbon, as at right of illustration, and wrap the ribbon in the opposite direction on the pencil it will be seen that the twist is uncoiled. This is the principle involved in the growth of the tendril. — Lehmanx Wendell.

���A Switchboard Operator Finds Time to Embroider

THE accompanying illustration shows how a busy telephone girl proves the truth of the old 'Where there's a will way." She has clamp attached

��axiom,

there's

had a

to the

��She is attending strictly to business and embroidering at the same time

��edge of her switchboard, to which is fastened a hooked ring to hold her embroidery frame. She has only to make her connec- tions when a call is received, and then her hands are free. She can talk through the mouthpiece while her hands are busy with the needle. In this way she not only fills her "hope chest" without wasting her employer's time, but she re- lieves the tedium ot the hours and the nerve strain.

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