REPORT OF THE SECRETARY 129 



This work differs from earlier work in that it is carried out with 

 entire plants instead of individual leaves cut from plants as pre- 

 viously used. The results presented must be regarded as simply 

 preliminary, since certain difficulties are yet to be overcome. These 

 experiments are preparatory for those contemplated wherein approxi- 

 mately monochromatic light will be used. The development of 

 equij^ment for this more elaborate experiment is nearing completion. 



In this work Doctor Johnston has carried out the physiological 

 phases of the experiment and Mr. Hoover has perfected the carbon 

 dioxide recording apparatus loaned to the division by the Fixed 

 Nitrogen Research Laboratory and has carried out the observations 

 with this instrument. 



2 4 6 8 10 IS t4 



I NTEMSITY 



FiGCRB 3. — Dependence of photosynthesis on light intensitj 



ALGAE INVESTIGATIONS 



As a result of the cooperation of the Department of Agriculture 

 Doctor Meier has been able to initiate a program of algae investi- 

 gations which will be extended through the following year as a 

 part of her work as National Research Council Fellow in the divi- 

 sion. Preliminary experiments have been carried out in which the 

 many special types of algae which she has collected have been sub- 

 jected to different nutrient solutions, and to different temperature 

 and illumination conditions, with a view to determining the condi- 

 tions required for the experiments contemplated. 



She has found that certain varieties may be grown in a colorless 

 condition in the dark and subsequently gain their normal coloration 



