REPORT OF THE SECRETARY 7 



country was conquered and his property lost, was retained on the 

 staff of the Observatory for 1 year through funds provided by John 

 A, Roebling. Soon after beginning his work Dr. Arctowski became 

 convinced of the reality of solar variation and that it is the major 

 factor in weather, and he published two papers summarizing his 

 findings. Dr. Abbot endeavored to evaluate the separate influences 

 produced on weather by long-range solar periodicities. It soon ap- 

 peared that considerable weather changes were produced by the peri- 

 odicities, and changes in phase of the weather responses were found 

 to be due to seasonal influences. Five-year forecasts, using only 

 meteorological periodicities antedating 1935, showed a marked corre- 

 lation between the forecast and the event. In the forecast for pre- 

 cipitation at Peoria, 111., a correlation coeflBcient of 70 ±5 percent was 

 found between prediction and event. It is hoped that further study 

 may improve the 5-year synthetic forecasts. 



Division of Radiation and Organisms. — In continuation of its 

 investigations on the relation of light to plant growth, the Division 

 carried forward a number of promising experiments, particularly in 

 the field of photosynthesis. A large number of simultaneous meas- 

 urements were made of the rate of carbon dioxide uptake and the 

 intensity of fluorescence during the induction period of photosyn- 

 thesis. These showed very interesting results, and further work 

 along this line is proposed, for it is felt that fluorescence is a useful 

 tool in the study of the mechanism of photosynthesis. Kespiration 

 and chlorophyll studies have been continued with the recording 

 spectrographic carbon dioxide apparatus. The perfecting of in- 

 struments and technique has progressed to a point where detailed 

 work on the problems relating to the genesis of chlorophyll and the 

 beginning of photosynthesis may be carried on. A standardized 

 technique has been worked out for the extraction of growth sub- 

 stances from the oat seedling which has proved to have a number 

 of advantages over other methods. A number of biochemical sub- 

 stances and plant extracts have been tested in the study of the growth 

 of excised oat shoots and leaves. The maximum light sensitivity of 

 the oat mesocotyl was shown to occur in the red region of the 

 spectrum. Algae exposed four times to stimulative amounts of cer- 

 tain wave lengths of ultraviolet light showed 4 to 4.8 times the 

 growth rate (expressed as number of cells) of the control cultures. 

 The stimulated cells were less sensitive to lethal amounts of ultra- 

 violet than the unstimulated cells. This and other results of experi- 

 ments on the effects of ultraviolet on algae will be published during 

 the coming year. Three papers by members of hte Division's staff 

 were published during the year. 



