o 



o 

 a: 

 o 



120- 



H 100 



z 



O 



>? 80 



60 



-30 







10 15 20 25 30 



TIME IN HOURS 

 Fig. 2. A. Time course of the effect of cobalt chloricie on the elongation of 10 

 mm. Avena coleoptile sections. All media contain sucrose 10 g/1, KCl O.OOIM and 

 lAA I mg/1 (=6.10-''i\/); all concentrations of cobalt indicated on the curves are x 

 10-°M; mean of 2 complete experiments, each including all 4 cobalt concentrations 

 and the control, and of 3 experiments at the 18i4 hour point. B. Time course of 

 the positive or negative increments due to cobalt, derived from the above. 



