518 



RHYTHMS IN PLANTS AND ANIMALS 



tion of the clock within a few days. Orange Hght, however, is very 

 favorable for the functioning of the clock (Bunning and Lorcher, 

 1957). 



INFLUENCE OF CHEMICAL FACTORS 



Several attempts have been made to discover the mechanism of 

 the endogenous periodicity by influencing it with chemical factors 

 (Bunning, 1935a, 1956a; Grabensberger, 1934; Kalmus, 1934, 1935, 

 1938; Renner, 1957). Kalmus in 1934 and 1935 produced a delay 

 of the clock in bees and in Diosophila by applying COj and by 



B 



Fig. 13. Phaseohis miiltiflonis, leaf movements in continuous light. A, 

 controls; B, 10-^ mole dinitrophenole, offered via the transpiration 

 stream during the whole experiment; C, 10"^ mole dinitrophenol offered 

 for the period marked by horizontal line; the rhythm comes back without 

 a shifting of the phases. = midnight. 



removing O2. Similar results with plants had been published by that 

 time (Biinning, 1935b). 



However, things appear very different if we check the influence of 

 chemicals for more than one period. In experiments of several days 

 duration we shall quite often find that the clock returns to the normal 



