Action spectra for delayed light production by several algae were determined from 250 to 750 mµ incident light.

In the visible portion of the spectrum the action spectra resemble those reported by previous workers for photosynthesis and light emission. Blue-green algae had a maximum at 620 mµ, red algae at 550 mµ, whereas green and brown algae have action spectra corresponding to chlorophyll and carotenoid absorption.

In the ultraviolet portion of the spectrum delayed light is emitted by algae down to 250 mµ incident light.

The action spectra of the different algae are not alike in the ultraviolet portion of the spectrum.

This indicates that pigments other than chlorophyll must be sensitizing or shielding the algae in the ultraviolet region.

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