#Effect of very low temperature.#--As regards the influence of very low temperature, I had opportunities of studying the question on the sudden appearance of frost. In the previous week, when the temperature was about 10 deg. C., I had obtained strong electric response in radishes whose value varied from .05 to .1 volt. But two or three days later, as the effect of the frost, I found electric response to have practically disappeared. A few radishes were, however, found somewhat resistant, but the electric response had, even in these cases, fallen from the average value of .075 V. under normal temperature to .003 V. after the frost. That is to say, the average sensitiveness had been reduced to about 1/25th. On warming the frost-bitten radish to 20 deg. C. there was an appreciable revival, as shown by increase in response. In specimens where the effect of frost had been very great, i.e. in those which showed little or no electric response, warming did not restore responsiveness. From this it would appear that frost killed some, which could not be subsequently revived, whereas others were only reduced to a condition of torpidity, from which there was revival on warming. I now tried the effect of artificial lowering of temperature on various plants. A plant which is very easily affected by cold is a certain species of Eucharis lily. I first obtained responses with the leaf-stalk of this lily at the ordinary temperature of the room (17 deg. C.). I then placed it for fifteen minutes in a cooling chamber, temperature -2 deg. C., for only ten minutes, after which, on trying to obtain response, it was found to have practically disappeared. I now warmed the plant by immersing it for awhile in water at 20 deg. C., and this produced a revival of the response (fig. 35). If the plant be subjected to low temperature for too long a time, there is then no subsequent revival. [Illustration: FIG. 35.--DIMINUTION OF RESPONSE IN EUCHARIS BY LOWERING OF TEMPERATURE (_a_) Normal response at 17 deg. C. (_b_) The response almost disappears when plant is subjected to -2 deg. C. for fifteen minutes. (_c_) Revival of response on warming to 20 deg. C.] I obtained a similar marked diminution of response with the flower-stalk of Arum lily, on lowering the temperature to zero.