452 



LIGHT AND LIFE 



spectra (10, 11). This C,,695 pigment is shown below to be the 

 form of chlorophyll a which, when activated together with chloro- 

 phyll /; in green algae or with phycobilins in red algae, is responsible 

 for the Emerson enhancement effect. 



Ca707, shown in Fig. 5, has occasionally appeared in abundance 

 in both Ochromonas danica (3) and Euglena gracilis (10) . The condi- 

 tions promoting its formation in large amounts are not at all under- 

 stood, but, like Ca695, its presence in smaller quantities is indicated in 

 some leaves and algae by analysis of their derivative absorption 

 spectra. Recent unpublished work of J. S. Brown has shown a corre- 

 lation of 707 m/7, absorption with the pheophytin content of the cells. 

 It may be that 707 m^u. absorption is due to a combined form of 



at 



%^ 



o 

 .a 



O 



o 



650 



700 



Wavelength,mfi 



Fig. I. the analysis of a derivative absorption spectrum of Ochromonas danica. 



Tlic indi\ idiial components arc derivatives of normal probability curves. The sum 



of tlicsc com|)oiuius is sliown as the dashed curve that very nearly matches the 



nieasiucd spectrum. The half widths of the components are given in parentheses. 



From {?,). 



