480 



LIGHT AND LIFE 



HE/ 



600 



650 



700 



?50 



Mn 



Fig. 1. Derivative absorption spectrum of a culture of Ochromonas danica show- 

 ing absorption at aroimd 710 m^. Obtained through the collaboration of Dr. C. 

 S. French. 



Ochromonas danica is an organism notable for the complexity of 

 its absorption spectrum of chlorophyll a in vivo and for the presence 

 in young healthy cells of a considerable proportion of a form of 

 chlorophyll a absorbing at 695 m^x (1). Integral absorption spectra 

 have at times been obtained showing a shoulder at 710 ni/x; in other 

 spectra this peak may not have been resolved from the 695 m^u, ab- 

 sorption. Fluorescence data support the conclusion that a pigment ab- 

 sorbing at wavelengths longer than that of chlorophyll is present 

 in this organism. As seen in Table 1, the fluorescence at 725 m,x is 

 much higher in relation to that at the chlorophyll absorption maxi- 

 mum in O. danica than in Chlorella or in chlorophyll a solutions 

 (O. danica contains no chlorophyll other than chlorophyll a). More- 

 over, there is no constancy of ratio between the absorption at 725 m^ix 

 and at the chlorophyll maximum, and the 725 m^it fluorescence is 

 high in samples in which absorption at 710 m^. is clearly shown. Since 

 there is no correlation between the amount of fluorescing pigment 

 present and the ratio of fluorescence at 725 m^ and the chlorophyll 

 maximum, it seems unlikely that these results are due to reabsorption 

 of fluorescent radiation. 



An absorption jieak at aroinul 710 m^u, has also been observed in 

 certain nuitants of Chlorella pyrenoidosa (Fig. 2) . The mutants in 

 which this has been observed are all of the type known as "apple 

 green," which contain chlorophyll a, in a quantity considerably less 



