In many of their properties the fungi are closely allied to some members of the animal kingdom. They resemble the flesh of animals in containing a large proportion of albuminous proximate principles; and produce in larger quantity than all other plants azote or nitrogen, formerly regarded as one of the principal marks of distinction between plants and animals. This element reveals itself by the strong cadaverous smell, which most of them give out in decaying, and also by the savory meat-like taste which others of them afford. Of all known bodies, nitrogen is the most unstable. Its compounds are decomposed by slight causes; and, therefore, its presence in the animal frame is the cause of its activity and proneness to change. To this circumstance also is owing the fugacious character of fungi, their speedy growth and decay. Unlike other vegetables, fungi possess the remarkable property of exhaling hydrogen gas; and the great majority of species, like animals, absorb oxygen from the atmosphere, and disengage in return from their surface a large quantity of carbonic acid. By chemical analysis, they are found to contain, besides sugar, gum, and resin, a yellow spirit like hartshorn, a yellow empyreumatic oil, and a dry, volatile, crystalline salt, so that their nature is eminently alkaline, like animal substances extremely prone to corruption. The cream-like substance, of which the family of Myxogastres is composed, resembles sarcode, and exhibits Amœba-like movements. Some of them contain such a quantity of carbonate of lime that a strong effervescence takes place on the application of sulphuric acid. Fungi feed like animals upon organic compounds elaborated by other plants. They contribute in no way as vegetables to the balance of organic nature. Another property they possess, which connects them with animals, is their luminosity. This quality is very rare among plants, and is almost peculiar to the lowest order of animals, particularly those which inhabit the ocean. A species of mushroom (Agaricus olearius) grows on the olive-tree which is often luminous at night, and resembles the faint, lambent, flickering light emitted by the scales of fish and sea-animals kept in a dark place. Anomalous conditions of various species of Polyporus, Hypoxylon, etc., formerly referred to the genus Rhizomorpha, from their root-like appearance, cover the walls of dark mines with long, black, branchy, flat fibres, and give out a remarkably vivid phosphorescent light, almost dazzling the eye of the spectator. In the coal mines near Dresden, these fungoid bodies are said to cover the roof, walls, and pillars with an interlacing network of beautiful, flickering light like brilliant gems in moonlight, giving the coal mine the appearance of an enchanted palace on a festival night.