“It is said that on summer evenings certain flowers appear to sparkle, phosphoresce, or radiate a momentary light. Some observers describe these occurences in more exact detail.

I had often sought to experience this for myself, even contriving several experimens in an attempt to produce it.

On the evening of June 19, 1799, I was strolling through the garden with a friend just as twilight was passing into cloudless night. We distinctly saw something flamelike appear close to some oriental poppies, a flower redder than any other. We stood in front of the plants and observed them closely but were unable to see anything more; at last we succeeded in repeating the effect at will by walking to and fro while looking at them sideways. It became evident that this was a phenomenon of physiological color and that the apparent flashing was really the afterimage of the flower in the required blue-green color.

Looking directly at a flower will not cause this phenomenon, although it will apear when the gaze wanders. Viewed obliquely, however, the flower produces a momentary double image in which the afterimage is seen just next to and touching the actual form.

In the dim light of dusk the eye is completely rested and receptive, while the color of the poppy is strong enough to maintain its full effect in the twilight of midsummer. Thus it can call forth a complementary image.”

—Johann Wolfgang von Goethe, from his Farbenlehre, or Theory of Color, 1808. Translated from the German by Douglas Miller, 1988.