340 
E. K. Hanson. 
the same plate), are H red (a=656), Na D (a=589-590), H green- 
blue, F (A=486), and H blue (a=434) : from which the phycoery- 
thrin fluorescence bands will be about a=656-630 and A=600-570. 
The absorption bands of chlorophyll differ in position some¬ 
what, according to the solvent used, but in any case these fluores¬ 
cence bands lie approximately on bands 1 and 3 of chlorophyll, as 
will be seen from the subjoined table. The values for chlorophyll 
are those quoted by Czapek. 1 
Phycoerythrin 
Chlorophyll Bands. Fluorescence 
In Leaf. In Alcoholic .Solution. Band. 
I. =700-654 ... 670-635 
II. =630-608 ... 622-597 
III.=600-578 ... 587-565 
655-630 
600-570 
A still more striking fact is that blue-green light produced the 
same fluorescence as white light. The blue-green light used was 
that of the same burner, filtered first through a special shade of 
green glass, obtained through the courtesy of the London and 
North Western Railway Signal Department, and then through a 
purple gelatine. This combination was successful in cutting out all 
red, orange and yellow light, whilst giving a fair intensity of the 
blue-green; the spectrum of this light is shown in Fig. 5. 
A decided orange fluorescence was visible when a beam of this 
light was passed through phycoerythrin solution, and the bands in 
the spectroscope were just visible to the eye. A very long exposure 
was necessary ; 30 hours gave no image, 70 hours only a very 
weak one, and the photograph shown (Fig. 4), had no less than 
210 hours’ exposure. The photograph shows a faint band of the blue- 
green light, no doubt due to reflection from the walls of the glass 
trough. This was not visible to the eye, nor on the photograph of 
70 hours’ exposure. 
There is thus no doubt that blue-green light does cause 
the orange fluorescence with bands in the same position as the 
chlorophyll absorption bands I. and III., and it therefore seems 
very probable that phycoerythrin does assist assimilation in the 
manner suggested, i.e., by absorbing the blue-green light and 
degrading it to yellow and red light of just those wave lengths 
which can be absorbed by chlorophyll. 
II.- Chemical Nature of Phycoerythrin. 
It has been suggested by Molisch- that phycoerythrin is protein 
1 Biochemie der Pflanzen, Vol. I., p. 455. 
2 Bot. Zeit., 1894. 52. 177. 
