Chap. I] CHARACTERS OF THE TROPICAL CLIMATE 221 



Wiesner has numerically determined the effects of direct sunlight on the 

 transpiration of rice plants at Buitenzorg ' : — 



EFFECT OF DIRECT INSOLATION ON TRANSPIRATION. 

 Rice Plant A. 



Transpiration 

 per hour. 



081 gram. 

 2-32 grams. 



7-45 „ 

 ic-57 „ 



* S sun completely hidden ; Sj sun visible in the sky, only as a bright vision ; S 2 sun 

 visible as a bright disk ; S 3 sun covered only by a light haze or a delicate veil of cloud ; 

 S 4 sun completely exposed. 



Rice Plant B. 



A series of observations on a sunny morning with a young (red) and 

 an old (green) leaf of Amherstia nobilis — the specimens stood with their 

 stalks in water — gave the following amount of transpiration in grams 

 per 100 grams of living weight: — 



EFFECT OF DIRECT INSOLATION ON TRANSPIRATION OF AMHERSTIA 



NOBILIS. 



Amount of transpiration in grams per 100 grams of living weight. 



Red leaf. Green leaf. 



Lender covered veranda . . . . 1-22 i-oo 



Free exposure, S . . . . . 1-88 2-56 



„ So 2-40 5-33 



S 4 3-1 1 8-44 



The following observations of Wiesner show how great transpiration can be at 

 Buitenzorg. He placed several herbaceous plants (Coleus, Adiantum, Jatropha, 

 Mimosa pudica) in pots, and imbedded them in the ground in a part of the garden 

 full)- exposed to the rain. For several days the plants received rain daily — sometimes 

 very heavy rain. ' On December 29 there was absolutely no rain ; the forenoon was 

 sunny, and at noon the sun was quite uncovered. On this day all the specimens — 

 they were not watered on the day in question — died of desiccation.' 



Giltay made comparative observations on the amount of transpiration of Helianthus 

 tuberosus at Buitenzorg and at Wageningen in Holland. They showed that the 



1 Recorded by Burgerstein, op. cit. 



