CLIMATE AND PLANT GROWTH. 

 WIND VELOCITY. 



25 



The wind velocity was measured automatically by anemometers 

 of the Weather Bureau pattern located about 15 feet above the 

 ground. 



SUNSHINE. 



The records of sunshine obtained were for both duration and 

 intensity. 



The duration of sunshine was recorded automatically by means 

 of the Marvin recorder used by the Weather Bureau. 



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AUGUST 19/6 



..... Difference between 6/ack ancf 

 white spheres 



Duration of sunshine 



Potentia/ Sunsh/ne /n hours 



Fig. 10. — Difference between black and white spheres in evaporation as compared with 

 hours of sunshine recorded by black bulb sunshine recorder. 



Data on sunshine intensity were obtained by noting the difference 

 in the evaporation between the radio-atmometer and the ordinary 

 white porous cup atmometers. 1 The radio-atmometer used was a 

 black sphere of the same size as the more common white form. 

 Owing to its color it absorbs considerable of the radiant energy fall- 

 ing upon it, functioning in this regard much the same as foliage of 

 ordinary plants. The white porous cup, on the other hand, absorbs 

 comparatively little radiant energy and is therefore not appreciably 

 affected by increased light intensity. Hence, while by night the 



1 Livingston, B. E. A radio-atmometer for comparing light intensity. Plant World, 

 14, No. 4: 96-99. 1911. 



