100 



A MONTANE RAIN-FOREST. 



The first test (table 39) involved two plants of Pilea nigrescens and 

 one of Peperomia turfosa. The series was run over night and through 

 one day in the light, and was then placed in darkness for 48 hours, 

 readings being taken each morning and evening. On comparing the 

 rates of relative transpiration for the first night and the averaged rates 

 for the day in the light, the latter will be found to be the lower of the 

 two. The rates for the first night were, however, considerably higher 

 than those for the two nights in the dark chamber. The averaged 

 rates for the day in the light are lower than the diurnal readings in the 

 dark chamber in the case of Pilea, but are higher in Peperomia. The 

 rates for the first and second days and for the first and second nights 

 in the dark chamber are in fairly close agreement. The evidence of 

 the two plants of Pilea is in agreement in showing an increase in 

 relative rate due to darkness, while Peperomia shows a decrease in rate. 



TABLE 40. Influence of darkness on transpiration. 



Amounts of transpiration and relative transpiration for five species, in the diffuse light 

 of the laboratory and in a dark chamber. 



The second experimental series (table 40) involved the five species 

 which have heretofore been mentioned: Pilea nigrescens, Peperomia 

 turfosa, Peperomia basellcefolia, Diplazium celtidifolium, and Asplenium 

 alatum. These plants were run in diffuse light on October 11, and three 

 days later were run in the dark chamber from mid-afternoon until 

 mid-morning of the following day, and again to mid-afternoon of the 

 second day. The time of taking these readings is such that nocturnal 

 and diurnal rates in the darkness can not be compared. A comparison 

 of the averaged rates for the seven readings in the light with the single 

 diurnal rate in the darkness shows that the darkness rate was higher 



