Floral colours and the physiology of vision

Summary

The flowers of the Morning Glory (Ipomea learii) exhibit a bright blue colour of almost spectral purity in daylight. Visual observations, confirmed by spectrum photographs, show that this visual sensation results from the removal of the yellow and orange radiations from the complete spectrum, the relative intensities of the red, green and blue-violet regions remaining unaltered. The effect observed may be interpreted as the result of the masking of the visual effect of the red and green sectors by the blue sector in the spectrum in these circumstances.