64 



A MONTANE RAIN-FOREST. 



second ; a secondary maximum in the late afternoon of the third day of 

 Experiment 4,at 6 o'clock, having a positive effect on the rate of Peperomia 

 basellcefolia, causing checks in the rate of fall of Asplenium, Diplazium, 

 and Peperomia turfosa, and failing to affect Pilea nigrescens. Very 

 pronounced rises of evaporation in the night are frequent at Cinchona 

 because of the nocturnal winds, and these rises are frequently accom- 

 panied by slight increases of transpiration, as may be seen in the case 

 of Dodoncea (Experiment 2, table 17, fig. 3) at 8 and 9 p. m., and in the 

 case of five species under simultaneous investigation (Experiment 5, 

 table 20, fig. 6) at midnight. The nocturnal rates of absolute transpira- 

 tion, as compared with the diurnal, are not usually very low. An ex- 

 amination of the curves for five species run through the 24 hours 

 (Experiment 5, table 20, fig. 6) shows that the lowest nocturnal read- 

 ings were related to the highest diurnal readings as indicated by the 

 following percentages: Diplazium, 44 per cent; Asplenium, 40 per cent; 

 Pilea, 36 per cent; Peperomia turfosa, 20 per cent; Peperomia basel- 

 lcefolia, 21 per cent. In Experiment 4 (table 19, fig. 5) the first reading 

 taken in the morning on the first and third days of the experiment 

 was an all-night reading, and its amount, determined at 6 a. m., may 

 be compared with maximum rate for one day, which was abnormally 

 low^ on the first day, but normal on the third. On tables 23, 24, and 25, 

 the all-night readings of transpiration are indicated, and their amounts 

 may be compared with the diurnal amounts for a number of experi- 

 ments with three species, and about the same relation will be found 

 to hold between nocturnal and diurnal rates as is indicated by the 

 above percentages, although occasional very low nocturnal rates are 

 registered. 



TABLE 16. Transpiration of Clelhra occidentalis and Alchornea latifolia. 



EXPERIMENT 1. Series run in open air with severed shoots, by potometer method. 

 Clethra, 9 leaves, area 234.5 sq. cm.; Alchornea, 13 leaves, area 376.9 sq. cm. 



