Figure 3. This photograph and the one below (Figure 4) show the effects 

 of temperature on the daily cycle of tomato plants. Here, at a temperature 

 of 15° C. (59° F.), the plant's internal rhythm is slowed so that it makes its 

 greatest growth with an external "day" of 27 hours. 



Figure 4. At a temperature of 30° C. (86° F.) the same variety of plants 

 achieves its greatest growth with a shortened "day" of 18 to 20 hours. 



