In order to find out whether subjection to hot water would kill the celery-stalk, I took it out and placed it for five minutes in water at 55 deg. C. This, as will be seen from the record taken afterwards, effectively killed the plant (fig. 38, w). [Illustration: FIG. 39.--EFFECT OF RISING AND FALLING TEMPERATURE ON THE RESPONSE OF SCOTCH KALE] #Increased sensitiveness as after-effect of temperature variation.#--A very curious effect of temperature variation is the marked increase of sensitiveness which often appears as its after-effect. I noticed this first in a series of observations where records were taken during the rise of temperature and continued while the temperature was falling (fig. 39). The temperature was adjusted by electric heating. It was found that the responses were markedly enhanced during cooling, as compared with responses given at the same temperatures while warming (see table). Temperature variation thus seems to have a stimulating effect on response, by increasing molecular mobility in some way. The second record (fig. 40) shows the variation of response in Eucharis lily (1) during the rise, and (2) during the fall of temperature. Fig. 41 gives a curve of variation of response during the rise and fall of temperature. TABLE SHOWING THE VARIATION OF RESPONSE IN SCOTCH KALE DURING THE RISE AND FALL OF TEMPERATURE Temperature Response Response [Temperature rising] [Temperature falling] 19 deg. C. 47 dns. -- 25 deg. " 24 " -- ^ 30 deg. " | 11 " 23 dns. | 50 deg. " | 8 " 16 " | 70 deg. " v 7 " -- -----> [Illustration: FIG. 40.--RECORDS OF RESPONSES IN EUCHARIS LILY DURING RISE AND FALL OF TEMPERATURE Stimulus constant, applied at intervals of one minute. The temperature of plant-chamber gradually rose on starting current in the heating coil; on breaking current, the temperature fell gradually. Temperature corresponding to each record is given below. Temperature rising: (1) 20 deg., (2) 20 deg., (3) 22 deg., (4) 38 deg., (5) 53 deg., (6) 68 deg., (7) 65 deg.. Temperature falling: (8) 60 deg., (9) 51 deg., (10) 45 deg., (11) 40 deg., (12) 38 deg..]