REPORT OF THE SECRETARY 63 



seem to have been found. Growth of tomato plants under control 

 as to temperature, humidity, and color and intensity of radiation are 

 in progress. The interesting and important observation was made 

 that these plants require a resting period at cooler temperature as 

 well as darkness. 



In cooperation with the United States Department of Agriculture, 

 experiments were made and published on the promotion and inhibi- 

 tion of the germination of seeds under different selected wave lengths 

 of light. 



An experiment on the growth of wheat under out-of-door condi- 

 tions with controlled quantities of carbon dioxide was carried 

 through with satisfactory results. 



Absorption spectral apparatus has been adjusted for use. 



A number of papers embodying the results of all of the above- 

 mentioned experiments were published during the year, and others 

 are in preparation for publication. 



Personnel. — No changes occurred, except that Dr. Enoch Karrer 

 was employed temporarily. 



Eespectfully submitted. 



C. G. Abbot, Director. 



The Secretary, 



Smithsonian Institution. 



