8-0 



6-0 



4-0 - 



2-0-- 



10 II 12 13 



LENGTH OF THE DARK PERIOD IN HOURS 



100 



© — I 



LENGTH OF DARK PERIOD IN HOURS 

 Figure 3-7 

 The flowering response of cocklebur plants exposed to various dark 

 period lengths, applied once or five times. A (top) shows response 

 plotted according to the system of Floral Stages described in Chapter 5. 

 B (below) shows response plotted as percentage of plants within a 

 treatment which flowered. The experiment was performed by the 

 advanced plant physiology class at Colorado State University beginning 

 May 14, 1962. Plants examined after 8 days. Data previously un- 

 published. 



