REPOET OF THE SECRETARY 19 



These results are so striking as to offer great hope that the rela- 

 tionship between solar variation and the weather may enable the 

 skilled meteorologist to forecast principal changes of weather far in 

 advance. 



In the hope of finding a site as satisfactory as Montezuma, Chile, 

 for solar observations, an expedition supported by John A. Roebling 

 and headed by A. F. Moore is now in the field testing various locali- 

 ties in Africa and outl.ying regions. 



DIVISION OF RADIATION AND ORGANISMS 



During the second year of the existence of the Division of Radia- 

 tion and Organisms, under direction of Dr. F. S. Brackett, a num- 

 ber of researches in physics and chemistry in connection with bio- 

 physics were begun. The phototropic experiments upon oat coleop- 

 tiles initiated during the previous year were continued with refine- 

 ment of technique by Doctors Johnston and McAlister. The purpose 

 of this investigation was to determine the phototropic response of 

 the oat coleoptile toward light of different colors, or of different 

 spectral regions, by means of light filters, and this year's more elab- 

 orate experiments showed results in striking agreement with the 

 rougher results of the previous year. 



Preliminary experiments on the carbon dioxide assimilation of 

 wheat plants were conducted by Doctor Johnson and Mr. Hoover, 

 using special all- vitreous growth chambers. Entire plants are used 

 instead of individual leaves as in earlier work, and a typical day's 

 run of the recording apparatus shows the carbon dioxide assimilated 

 for different light intensities. Equipment is being developed for 

 more elaborate experiments using approximately monochromatic 

 light. 



Through the cooperation of tlie Department of Agriculture, Doc- 

 tor Meier has carried out preliminary experiments on the growth 

 of algse under controlled illumination and temperature conditions, a 

 part of her work as National Research Council Fellow in the division. 

 By the use of a large quartz spectrograph, the modifications in 

 growth rate or resulting death point may be observed comparatively 

 for different wave lengths of light. 



With the further cooperation of the Department of Agriculture, 

 in connection with the crop physiology and breeding investigations 

 of Doctor Swingle, of the Bureau of Plant Industry, Doctor Meier 

 and members of the division have carried on researches on the effects 

 of controlled radiation, humidity, and temperature on certain tropi- 

 cal and xerophytic plants. It was found possible to maintain con- 

 ditions that yielded for date palms ten times greater growth rate 

 102992—32 3 



