106 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1938 



nection with the C0 2 absorption studies and the formation of 

 chlorophyll. 



Among other projects, photosynthesis in algae is to be investigated. 

 In preparation for this research Dr. Johnston and Dr. Meier have 

 been testing various methods of producing thin coatings of living 

 algae on rods and plates, without the interposition of water layers 

 between the algae and such light source as may be employed. Success- 

 ful cultures of this sort have been made. 



Dr. Meier had a very serious fall in early December 1937 and was 

 incapacitated until June 1938, but returned to work part time in June 

 and full time in July. Prior to her accident she made further ob- 

 servations on stimulation of multiplication of algae by ultraviolet 

 rays which in larger dosage would be lethal. While the results ob- 

 tained certainly point strongly to a positive conclusion, further 

 work must be done before publication. 



Dr. Johnston has continued investigations on mixtures of artificial 

 lights suitable to promote fully satisfactory plant growth under 

 laboratory conditions. 



Dr. McAlister has made prolonged further studies on the depend- 

 ence of the induction periods in the photosynthesis of wheat on the 

 length of previous dark exposures. In addition, an uptake of C0 2 by 

 leaves in darkness has been discovered which has an important bear- 

 ing on photosynthesis. These phenomena are held by students of 

 photosynthesis to be of the greatest possible interest in obtaining an 

 understanding of the fundamental reactions which occur in plants 

 under the influence of light. Until the perfection of the technique by 

 Dr. McAlister, and his introduction of spectroscopy, as a highly 

 sensitive means of instantaneously measuring carbon dioxide assimila- 

 tion, the subject was practically beyond the possibility of investiga- 

 tion. But during the past year he has accumulated great numbers 

 of results which are the foundation of a paper he will shortly publish 

 under the title: "Chlorophyll — C0 2 ratio during photosynthesis," 

 which it is believed will be of the very highest interest to students of 

 this subject. As heretofore the technical work of the Division has 

 been ably promoted by Messrs. Clark and Fillmen. 



As noted under the Report on the Astrophysical Observatory, Mr. 

 Hoover has made interesting experiments at Mount Wilson, Calif., on 

 growing plants to maturity in narrow ranges of spectrum selected 

 from the sunbeam. This work will be described in next year's report. 



The following publications have been issued from the Division 

 during the fiscal year : 



Johnston, Eael S. 



Phototropic response and C0 3 assimilation of plants in polarized light. 

 Smithsonian Misc. Coll., vol. 96, No. 3. 1937. 



