774 Bose. — On Diurnal Variation of 
traceable to individual peculiarities. As an example of this, I give a record 
(Fig. 1 5) obtained with a specimen in which nyctitropic movement was very 
pronounced. The periodic variation of excitability exhibited here is practi- 
cally the same as shown by other specimens. The interesting variation is 
in the character of the recovery from stimulus ; the leaf was falling from 
6 to 9 p.m. ; owing to the shifting of the base-line upwards the recovery 
appears to be incomplete. After 9 p.m. the leaf was erected, at first slowly, 
then at a very rapid rate. The consequent fall of the base-line late at night 
Fig. 15. Record of diurnal variation of excitability : it exhibits marked nyctitropic movement. 
is very abrupt ; hence there is an apparent overshooting in the line of 
recovery. 
So far I have merely described the observed diurnal variation of * 
excitability. We may next inquire whether there is any causal relation 
between the change of external conditions and the observed variation of 
excitability. It has been shown that the moto-excitability is greatly 
influenced by temperature. In order to find in what manner the diurnal 
variation of excitability was influenced by the daily variation of tempera- 
ture, I took special care to secure by means of the thermograph a continuous 
record of temperature variations. The table which follows shows the relation 
between the hours of the day, temperature, and amplitude of response, in 
