52 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1933 



conditions of radiation, and R. M. Clagett has assisted with the wood 

 work of special devices. 



During the earlier part of the fiscal year, six pamphlets were pub- 

 lished under the following titles: 



Lethal action of ultra-violet light on a unicellular green alga, by Florence E. 

 Meier. 



A spectrophotometric development for biological and photochemical investiga- 

 tions, by F. S. Brackett and E. D. McAlister. 



The functions of radiation in the physiology of plants. I.|General methods 

 and apparatus, by F. S. Brackett and E. S. Johnston. 



The functions of radiation in the phj^siology of plants. II. Some effects of 

 near infrared radiation on plants, bj' Earl S. Johnston. 



Carbon dioxide assimilation in a higher plant, by W. H. Hoover, Earl S. 

 Johnston, and F. S. Brackett. 



Absolute intensities in the visible and ultra-violet spectrum of a quartz mercury 

 arc, by E. D. McAlister. 



An outstanding exhibition was prepared for the Atlantic City 

 meeting of the American Association for the Advancement of Science 

 in December 1932, which attracted wide and favorable notice. Also 

 an interesting exhibit for the Century of Progress Exposition at 

 Chicago was prepared in cooperation between the division, the 

 Astrophysical Observatory, and the Division of Mineralogy of the 

 National Museum. 



In March 1933 a reorganization of the division took place. The 

 Secretary, Dr. Abbot, who has been engrossed in the preparation of 

 volume 5 of the Annals of the Astrophj^sical Observatory and volume 

 12 of the Smithsonian Scientific Series, having finished these tasks, 

 undertook the general charge of the division. Dr. F. S. Brackett 

 received a part-time appointment as consulting physicist with oppor- 

 tunity to devote himself entirely for the division on the investigation 

 of absorption spectra of organic substances such as contribute to the 

 chemical activity of plants. Dr. E. S. Johnston was appointed 

 assistant director of the division. 



Having completed his share of the preparation of the two exhibits, 

 Mr. Hoover carried through a study of the growth of wheat under 

 measured concentrations of water vapor and carbonic acid with fixed 

 temperature and illuminated by measured quantities of light from 

 helium discharge tubes. This research showed that the helium 

 discharge produces approximately 30 percent greater assimilation of 

 carbon dioxide than does equally intense white light. By means of 

 filters some progress was made by Mr. Hoover in separating the 

 effects of the several monochromatic rays of which the light of the 

 helium discharge tube is composed. 



Dr. McAlister, at the request of Dr. Abbot, undertook to devise a 

 better means of producing substantially monochromatic light of any 

 desired wave length for use in plant-growth experiments. After 



