Page:Life Movements in Plants.djvu/231

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MECHANICAL STIMULUS ON GROWTH
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minutes, the rate became 0.14 μ per second; after an hour the recovery was complete, the rate being now 0.18 μ per second, the normal rate before stimulation (Fig. 74a). We shall presently see that not only is the growth rate greatly depressed under intense stimulation, but the period of recovery also becomes very much protracted.

I have often been puzzled by the fact, that specimens apparently vigorous exhibited little or no growth, after attachment to the recorder. After waiting in vain for an hour, I had to discard them for others with equally unsatisfactory results. One of these specimens happened to be left attached to the recorder overnight, and I was surprised to find that the specimen, which had shown no growth the
Fig. 74.—(a) N, normal rate of growth; F, retarded rate immediately after friction; A, partial recovery after 15 minutes.
(b) N, normal; W, immediately after wound; C, an hour after. (Successive dots at intervals of 5″.) previous evening, was now exhibiting vigorous growth after being left to itself for 12 hours. I then realised that the

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