1. The delayed light emission of Chlorella pyrenoidosa over the wave length range 400 to 950 mµ has been investigated.
2. Emission of delayed light is confined to the range 600 to 800 mµ.
3. To the precision with which the low light intensities involved can be measured with the apparatus in these experiments, the emission spectrum of the delayed light is the same as the spectrum of the fluorescent light.
4. Thus the delayed light must come from excited chlorophyll.