TRANSPIRATION BEHAVIOR OF RAIN-FOREST PLANTS. 



63 



single pronounced maximum, while the recurrence of sunshine is 

 frequently responsible for a second rise and sub-maximum (Experi- 

 ments 2 and 3). The occurrence of a sub-maximum before the actual 

 maximum of the day is rare. A slight increase of the evaporation rate 

 in the early afternoon may be accompanied by a relatively pronounced 

 increase of the transpiration, as occurred at 1 p. m. and 3 p. m. in Exper- 

 iment 3. The later in the afternoon such secondary maxima of evap- 

 oration occur, the less is the response of the transpiration rate : such a 



CLEAR HI] 

 CLOUDY 

 FOG 



RAIN E21 

 NIGHT 



FIG. 2. Daily march of transpiration in Clethra (TC) and Alchornea (TA), together 

 with concurrent rate of evaporation ( ) , rates of relative transpiration for the 



TC TA 



two plants, r and -=- respectively, and schematic depiction of weather conditions. 

 E L/ 



maximum in Experiment 3 at 6 p. m. affecting neither Pilea nor Peperomia 

 (table 18, fig. 4) ; slight secondary maxima in Experiment 2 affecting 

 Dodoncea slightly on the first day of the experiment and not at all on the 



