Observations on Phycoerythrin. 
339 
The Part Played by Phycoerythrin in Assimilation. 
As the algae in which phycoerythrin occurs contain also chloro¬ 
phyll, and yet live at a depth where the light reaching them is largely 
deprived of that portion of the spectrum most efficient in forwarding 
assimilation in chlorophyll-bearing plants, it has been suggested 
that the role of phycoerythrin is to aid assimilation by handing on 
the energy derived from the absorption of the light reaching the 
depths at which these algae grow. If this is so, the absorption 
spectrum of phycoerythrin should exhibit marked absorption of the 
blue-green light which is available in deep water, and, further, it 
must in some way transmit the energy thus obtained to the chloro¬ 
phyll. From the deep orange fluorescence it is conjectured that 
phycoerythrin absorbs the blue-green light and degrades it to yellow 
and red which can be absorbed in turn by the chlorophyll. 
The absorption spectrum of phycoerythrin has been exhaustively 
studied by F. Schtitt, 1 and it has been shown that phycoerythrin 
does indeed absorb that part of the spectrum which penetrates deep 
water. A photograph of the phycoerythrin absorption spectrum is 
shown in Plate V., Fig. 2. 
Schiitt 2 has also shown that only light of wave-length 600-486 
has the power of exciting fluorescence in phycoerythrin solutions, 
and advances the opinion that the fluorescent light is probably 
about 590-560, i.e., near the sodium (D) line. But no exact deter¬ 
mination appears to have been made, up to the present, on the 
fluorescence, and so the fluorescent light from phycoerythrin solution 
was photographed. 
The method employed was to send a beam of light through a 
trough containing phycoerythrin solution and to place the spectro¬ 
scopic camera at right angles to the path of the beam. “ Pan¬ 
chromatic ” plates were used which were almost equally sensitive 
to all parts of the spectrum, though slightly over-sensitive to the 
far red. Using white light from an inverted incandescent gas 
burner of 80 candle power, a marked fluorescence was obtained, the 
spectrum of which was easily visible to the eye, and was photographed 
by an exposure of ten hours (Fig. 3). It will be seen that the 
fluorescence gives two well-marked bands, one about the D line and 
the other near the hydrogen red. These bands appear to be related 
to the absorption bands of chlorophyll. 
The reference lines in the upper spectrum, Figure 1 (taken on 
1 Ber. deut. bot. Gesell., 1888, VI., 1, 36. 
1 Ber. deut. bot. Gesell., 1888, VI., 8, 307. 
