“On the 19th of June, 1799, late in the evening, when the twilight was deepening into a clear night, as I was walking up and down the garden with a friend, we very distinctly observed a flame-like appearance near the oriental poppy, the flowers of which are remarkable for their powerful red colour. We approached the place, and looked attentively at the flowers, but could perceive nothing further, till at last, by passing and repassing repeatedly, while we looked side-ways on them, we succeeded in renewing the appearance as often as we pleased. It proved to be a physiological phenomenon, and the apparent corruscation was nothing but the spectrum of the flower in the complementary blue-green colour. The twilight accounts for the eye being in a perfect state of repose, and thus very susceptible, and the colour of the poppy is sufficiently powerful in the summer twilight of the longest days to act with full effect, and produce a complementary image.”[110] The leaves of the _œnothera macrocarpa_ are said to exhibit phosphoric light when the air is highly charged with electricity. The agarics of the olive-grounds of Montpelier have been observed to be luminous at night; but they are said to exhibit no light, even in darkness, _during the day_. The subterranean passages of the coal mines near Dresden are illuminated by the phosphorescent light of the _rhizomorpha phosphoreus_, a peculiar fungus. On the leaves of the Pindoba palm, a species of agaric grows which is exceedingly luminous at night; and many varieties of the lichens, creeping along the roofs of caverns, lend to them an air of enchantment by the soft and clear light which they diffuse. In a small cave near Penryn, a luminous moss is abundant; and it is also found in the mines of Hesse. According to Heinzmann, the _rhizomorpha subterranea_ and _aidulæ_ are also phosphorescent. It is but lately that a plant which abounds in the jungles in the Madura district of the East Indies was sent to this country, which, although dead, was remarkably phosphorescent; and, when in the living state, the light which it emitted was extraordinarily vivid, illuminating the ground for some distance. Those remarkable effects may be due, in some cases, to the separation of phosphuretted hydrogen from decomposing matter, and, in others, to some peculiar electric manifestation.