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rate being new reduced to 0'15 a per second. These effects were found to take place equally in light or in darkness.

(Ian Gas.- ly‘J-periment 66.#Coal gas induces a depres- sion. 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.

Sulphm'ettwd Hydrogen: ﬂrpem'ment 67.——-This gas not only exerts a depressing 0th ct, hut. 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 reeoVery.

Ammnm‘um Sulpln'de: 141.1'1wr1'ment 68.——This reagent in dilute solution retards growth, and in stronger solution acts as a poison. The following results were obtained with a “heat seedling under dill‘erent strengths of solution :—-

Normal rate 0'30 [1. per sec. (W) per cent. solution 0'15 ,1. ,, ., 23‘“ ,. ,, ,, 0'08 p. ,, ,,

Popper Sulphate: I'Lrperiment 69.~—The effect of a solu- tion of this reagent is far more depressing than the last. One per rent. solution acting for a short time depressed