ENDOGENOUS DIURNAL PERIODICITY 



517 



3 

 DAYS 



DAYS 



Fig. 12. Phaseolus nuilliflonis, leaf movements in continuous light. 

 Irregular periodicity with temperatures of 10°C. In A, two cycles with 

 normal length. (After BUnning and Tazawa, 1957.) 



found no modification in the length of periods between 6° and 29 °C. 

 Temperatures of 0° to 3°C, however, prevented the functioning of the 

 clock completely, that is. the rhythm became out of phase afterward 

 for the time of chilling to this temperature. The same holds true for 

 insects (Kalmus, 1934; Renner, 1957; cf. Addendum). 



INFLUENCE OF LIGHT ON LENGTH OF PERIOD 



With constant external conditions, the length of the period is differ- 

 ent in continuous dark and in continuous light of different qualities 

 (Table VII). Moreover, with higher plants, far red inhibits the opera- 



