C. STACY FRENCH 



65 



fluorescence peaks of protochlorophyll which may exist in the plant in 

 two forms — one having an absorption peak at 635, the other at about 

 650 m/x. This explanation would be hard to believe were it not for 

 the recent experiments of Dr. Smith in which he has clearly shown 

 by absorption measurements the conversion of the 650-m/i, form in 

 freshly ground dark-grown barley leaves suspended in glycerin to the 

 635-m/x form in suspensions that have been heated or allowed to 

 stand. 



600 



650 700 



WAVELENGTH 



750 mji 



Fig. 14. Fluorescence spectrum of the inner seed coat of a banana squash. ( Hill, 

 Smith, and French, unpubhshed. ) 



The fluorescence spectrum of a dark-grown leaf exposed to light 

 for a short period of time is given in Fig. 15. Here we can clearly 

 distinguish the fluorescence spectrum of protochlorophyll in the pres- 

 ence of a considerably larger amount of chlorophyll. Dr. Hemming 

 Virgin is at present looking into the possibility of using such curves 

 for the quantitative measurement of rates of protochlorophyll trans- 

 formation to chlorophyll in living leaves. He has found that much 

 more reproducible results may be obtained by infiltrating the leaves 



