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LIFE MOVEMENTS IN PLANTS

region of growth. The specimen is then enclosed in a glass cylinder, with inlet and outlet pipes. The cylinder is first filled with water, and the normal rate of growth recorded. This rate remains constant for several hours; but prevention of access of air for too long a time affects the normal growth. After obtaining normal record, water charged with the giving chemical agent is passed into the cylinder; and the subsequent record shows the characteristic effect of the reagent. The introduction of a gas into the chamber offers no difficulty.

EFFECT OF STIMULANTS.

Hydrogen Peroxide: Experiment 62.—This reagent, as supplied by Messrs. Parke Davis & Co., was diluted to 1 per cent. and applied to the growing plant. Its stimulating action on growth is demonstrated in the right hand record of Fig. 68a, where the rate of growth is soon enhanced two and a half times the normal rate.

Fig. 68.—Effect of chemical agents: (a) Acceleration of growth under H2O2, (b) Effect of NH3, preliminary acceleration followed by retardation. (c) Effect of ether (E) and recovery (A).

Ammonia: Experiment 63.—The immediate effect of dilute vapour of this reagent is an enhancement of growth,

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