DITTRBAL THERMONASTIC MOVEMENT 553 



at night. Though the temperature continued to fall, there 

 was no possibility of further expansion beyond the maxi- 

 mum. The temperature began to rise after passing through 

 the minimum at 6 a.m., and the movement of closure 

 set in with rising temperature, the flower becoming com- 

 pletely closed by 10 a.m. That geotropism has little 

 effect is seen from the fact that the inversion of flower 

 does not interfere with the normal opening or closing of 

 the flower. 



The phenomenon of diurnal movement of Nymphcea is 

 therefore thermonastic, the floral leaves exhibiting move- 

 ment of opening at night owing to fall of temperature. 

 Luffa acutangula, which opens in the afternoon, and 

 closes early in the morning, gives a diurnal record similar 

 to that of Nymjihceu. 



SUMMARY. 



The flower of Nymphcea exhibits a movement of closure 

 during rise of temperature, and of opening during fall 

 of temperature. 



It is shown further that the effects of light and of 

 rise of temperature are antagonistic to each other. Light 

 is shown to induce in Nymphcea the movement of open- 

 ing, and darkness to cause the movement of closure. 

 The diurnal movement of Nymphcea is not therefore due 

 to periodic variation of light and darkness, but to the 

 predominant effect of variation of temperature. 



The diurnal record shows that the perianth leaves begin 

 to open in the evening with failing temperature, and the 

 flower becomes fully expanded by 10 p.m. The move- 

 ment of closure sets in with rising temperature in the 

 morning, and the flower becomes fully closed by 10 a.m. 



40 A 



