222 



ZONES AND REGIONS 



[Pt. Ill, Sect. I 



daily loss of water was the same in both cases, namely on the average o-6 gram 

 per hour, but even in this case transpiration during the hot midday hours appears to 

 have been much stronger in Buitenzorg than in Holland. 



Experiments made by G. Haberlandt at Buitenzorg in January, which 

 is the middle of the rainy season, and at Gratz during the hot days of 

 August, showed that transpiration in the shade in a moist tropical climate 

 is much weaker than in Central Europe : — 



The humidity of the air fluctuated at the time when Haberlandt made his experi- 

 ments (December, January), between 70-97 %. ' The minimum (70-80 %) occurred at 

 about midday, but frequently not till 1 p.m. Then the humidity increased rapidly 

 as the rain began, and even by 3 or 4 p.m. attained 90-95 %. Omitting slight 

 fluctuations, which seldom exceeded 5 %, the curve in its typical course remained 

 from the evening till about 7 a.m. at 93-97 %, and then gradually sank again till 

 noon V The temperature during the period of observation showed a diurnal variation 

 of 6-8° C. 



'The diurnal curve of temperature, as a rule, showed the following course: — 

 Between 6 and 7 a.m. the temperature was lowest. The minimum varied, omitting 

 extreme cases, between 21 and 23 C. During the forenoon the temperature at first 

 rose rapidly, then somewhat more slowly up to 29-30-5° C. This maximum was 

 rarely attained by midday, usually not till between 1 and 2 p.m. Then the tempera- 

 ture fell to 23-25°, sometimes more rapidly, at others more slowly, according to the 

 cloudiness, or amount and duration of the rainfall in the afternoon.' 



AMOUNT OF TRANSPIRATION OF LEAVES IN BUITENZORG 

 AND IN GRATZ (after G. Haberlandt 2 ). 



(In grams per diem and over one square decimeter of surface.) 



Haberlandt, I, p. 6. 



II, p. 807. 



