456 



LIGHT AND LIFE 



pation of accessory pigments were made long ago by Engelmann. The 

 precise work of Emerson and Lewis (17, 18), of Haxo and Blinks 

 (33), of Tanada (56), and of Yocum and Blinks (61), in which the 

 absorption was compared with the action spectra, has substantiated 

 Engelmann's conclusions and resulted in the remarkable discovery 

 of inactive chlorophyll in the red algae. Most of this work is too 

 well known to require further discussion here, but Fig. 7 (from 

 Haxo and Blinks) is given to show an example of action and ab- 



Fig. 



400 



440 



480 



920 



560 



600 



640 



680 



720 



760 



Wavelengfh,mjL/ 



7. The action and absorption spectra ot a red alga showing more photosynthesis 

 by phycoerythrin than by chlorophyll. From Haxo and Blinks (33). 



sorption measurements on the same sample. Some of the principles 

 and techniques useful in such measurements have been reviewed 

 (21, 29, 30). 



Automatic Recording of Action Spectra 



After the 695 nifx. form of chlorophyll had been found in Eiiglena, 

 the question arose as to its possible participation in photosynthesis 

 with energy acquired either by direct absorption or through energy 

 transfer. Largely lor this reason we thought the time had come to 

 ijtiild a device that had been in miiul lor some time. This is a 

 recording spectrojjhotouictcr to plot action spectra with somewhat 



