5.5
50 deg. 4
65 deg. 3

In radishes response disappeared completely at 55 deg. C., but with celery,
heated in the manner described, I could not obtain its entire abolition
at 60 deg. C. or even higher. A noticeable circumstance, however, was the
prolongation of the period of recovery at these high temperatures. I
soon understood the reason of this apparent anomaly. The method adopted
in the present case was that of dry heating, whereas the previous
experiments had been carried on by the use of hot water. It is well
known that one can stand a temperature of 100 deg. C. without ill effects in
the hot-air chamber of a Turkish bath, while immersion in water at
100 deg. C. would be fatal.

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 " |