Page:Life Movements in Plants.djvu/216
rate being new 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.
ACTION OF POISONS.
Ammonium Sulphide: Experiment 68.—This reagent in dilute solution retards growth, and in stronger solution acts as a poison. The following results were obtained with a wheat seedling under different strengths of solution:—
| Normal rate | … | 0.30 μ per sec. |
| 0.5 per cent. solution | … | 0.15 μ per„ sec.„ |
| 2.0 per„ cent.„ solution„ | … | 0.08 μ per„ sec.„ |
Copper Sulphate: Experiment 69.—The effect of a solution of this reagent is far more depressing than the last. One per cent. solution acting for a short time depressed