REPOIIT OF THE SECRETARY 105 



curve of cliloropliyll absorption. Wave-length regions inhibiting 

 germination were found in the blue and in the infrared spectrum. 



Dr. E. S. Johnston continued with marked progress his investiga- 

 tions tending to produce normal growth of tomato plants under lab- 

 oratory conditions. The great difficulty is to obtain from artificial 

 sources light of sufficient intensity and proper wave-length distribu- 

 tion. By various ingenious exiDcdients he has to a considerable degree 

 solved the problem. 



He also continued phototropic experiments, studying the bending 

 of plants toward the light as well as carbon dioxide assimilation 

 with polarized as compared to normal light. It had been sug- 

 gested that a real difference Avould be found, but he found none. 



With Dr. P. R. Burkholder, of Connecticut College, Dr. Johns- 

 ton investigated the inactivation of plant growth substance by light.* 

 A very beautiful teclmique Avas developed, whereby live tips and 

 half tips of oat seedlings were applied in various ways to decapi- 

 tated oat seedlings in order to determine what are the circum- 

 stances which govern elongation under the influence of light. The 

 results appear to show that under considerable intensities of light 

 the growth hormones are inactivated rather than displaced in pro- 

 ducing the well-known lower stature of illuminated plants as com- 

 pared with plants grown in semidarkness. For further informa- 

 tion see their very interesting paper. 



Dr. Meier did much work on the classification of a large col- 

 lection of algae for the National Herbarium. Her own investiga- 

 tions concerned a search for the stimulation of multiplication in 

 algae by ultraviolet rays known to be lethal in doses of sufficient 

 intensity. The research is not finished as yet, but plainly shows 

 great stimulative influence by minute doses of these lethal rays, 

 and that the degree of stimulation is most interestinglj'^ connected 

 both with wave length and with the lethal dosage. 



The instrument maker, Mr. Fillmen, and the glass technician, 

 Mr. Clark, constructed apparatus of invaluable use in these inves- 

 tigations. 



Respectfully submitted. 



C. G. Abbot, Director. 



The Secretary, 



Smithsonian Institution. 



* Smithsonian Misc. Coll., vol. 95, no. 20, pp. 1-14, fig. 1, pis. 1, 2, 1937. 



