EFFECT OF ANÆSTHETICS.
Fig. 69.—Effect of CO2. (a) Normal record; (b) immediately after application of CO2, and (c) 15 minutes after.
Ether: Experiment 64.—In Fig. 68c, the records exhibit the effect of introduction of ether vapour into the plant chamber, and its recovery after the removal of the vapour. Ether is seen to depress the rate of growth to a little more than a third of the normal rate. The recovery is seen to be nearly complete half an hour after the removal of the vapour.
Carbonic Acid: Experiment 65.—The action of this gas is very remarkable. The plant was immersed in water and normal record taken; the plant chamber was now filled with water, charged with carbonic acid gas. This induced a very marked acceleration of growth (Fig. 69). In a seedling of Onion, the increase was found to be two and a half times. In the flower bud of Crinum, the rate was found enhanced threefold from the normal 0.25 µ to 0.75 µ per second. After this preliminary enhancement, there was a depression of growth within 15 minutes of the application, the rate being now reduced to 0.15 µ per second. These effects were found to take place equally in light or in darkness.
ACTION OF DIFFERENT GASES.
Coal Gas: Experiment 66.—Coal gas induces a depression. It is curious that subjection to the action of this gas does not produce so evil an effect as one would expect. The introduction of the gas had reduced the growth-rate to more than half; but there was a recovery half an hour after the introduction of fresh air.
Sulphuretted Hydrogen: Experiment 67.—This gas not only exerts a depressing effect, but its after-effect is also very persistent. The plant experimented on was very vigorous and its rate of growth was depressed to half by subjection to the action of the gas for a short time. The record taken half an hour after the introduction of fresh air did not exhibit any recovery.