Chai'. I] CHARACTERS OF THl': TROPICAL CLIMATE 221 



Wiesncr 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. 



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

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

 S, sun completely exposed. 



Rice Pl.\nt B. 



Hours of experiment. Temperature. 

 8.43— 9.00 26.2° 



9 — 9-15 27° 



9.18— 9.34 27.2° 



9.39— 10.10 27° 



A series of observations on a sunn\- morning with a \'oung (red) and 

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

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

 )er 100 grams of living weight; — 



■:FFECT of direct INS0L.A.TI0N on TRANSPIR.JlTION OF AMHERSTIA 



NOBILIS. 



Amount of transpiration in grains per loo grams of living weight. 



Red leaf. Green leaf. 



Under covered veranda . . . . 1.22 i.oo 



Free exposure, Sj, 1.88 2-56 



S., 2-40 5.33 



S, 3-11 8-44 



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

 iuitenzorg. He placed several herbaceous plants (Coleus, Adiantuni. Jatropha, 

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

 illy e.xposed to the rain. For several days the plants received rain daily — sometimes 

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

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

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



Giltay made comparative observations on the amount of transpiration of Helianthus 

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



' Recorded by Burgerstein, op. cit. 



