222 CHAP. XX. THERMONASTIC MOVEMENT 



at night. Though the temperature continued to fall, 

 there was no possibility of further expansion beyond the 

 maximum. The temperature began to rise after passing 

 through the minimum about 5 a.m., and the movement of 

 closure set in with the rise of temperature till the flower 

 became completely closed by 10 a.m. (fig. 130). 



Fig. 130. Diurnal record of Nymphaea. 



Upper record gives variation of temperature ; the up-curve 

 representing fall, and down-curve rise of temperature. The 

 lower record exhibits the movement of the flower, up-curve 

 representing the opening, and down-curve the closure of 

 the flower. 



The phenomenon of diurnal movement of the Water- 

 Lily is therefore thermonastic, the floral leaves exhibiting 

 a movement of opening at night owing to fall of temperature. 

 The outer side is the more active. 



The Water-Lilies of Europe close at night and open in 

 the daytime. In searching for an Indian Water-Lily 

 resembling the European type, I was successful in dis- 

 covering a blue Lily, the diurnal record of which is exactly 

 the opposite. In such cases it is the inner side that is 

 relatively the more sensitive. 



