APPENDIX 8 



KEPORT ON THE DIVISION OF RADIATION AND 

 ORGANISMS 



Sir: I have the honor to submit the following report on the activi- 

 ties of the Division of Radiation and Oriranisms during its second 

 year ending June 30, 1931. 



RESEAECII IN PROGRESS 



Building around the central idea of a laboratory combining experi- 

 mental work in biophysics with fundamental experimentation in 

 physics and chemistry, researches have been carried forward in both 

 these fields. The phototropic experiments upon oat coleoptiles 

 previously reported have been carried further with considerable 

 refinement of technique. The carbon dioxide assimilation of wheat 

 has been studied as a function of intensity in artificial light. Pre- 

 liminary experiments with algae have been initiated with a view to 

 determining carbon dioxide assimilation as a function of wave length 

 and intensity, growth rate as a function of wave length and inten- 

 sity, and death point as a function of wave length, and time-intensity 

 dosage. The propagating chamber which was developed by the 

 division has been used in cooperation with the Department of Agri- 

 culture for the purpose of investigating the effects of artificial light, 

 humidity, and temperature upon the growth of certain desert and 

 tropical plants. 



In the field of pure physics and physical chemistry the major 

 part of the time has been devoted to the development of the necessary 

 equipment for the general intensity and infra-red work contemplated. 

 The intensity distribution in the mercury spectrum has been deter- 

 mined directly. In cooperations with the Fixed Nitrogen Research 

 Laboratory the spectra of HCl, HCN, and the halogen substitution 

 products of benzene have been investigated in the region between the 

 visible and 2/x. 



PHOTOTROPISM 



In a preliminary experiment the phototropic response of the oat 

 coleoptile toward light was determined comparatively for different 

 colors or spectral regions by means of light filters. The results of 

 this experiment may be conveniently summed up in the accompjiny- 



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