FOOT — ON ANIMAL LUMINOSITY. 43 



fied structure points which possess an irregular phosphorescence, 

 sometimes rising to such a degree as to enable surrounding objects to 

 be distinguished.* The species of Rhizomorphoe are numerous in the 

 coal mines in the vicinity of Dresden, and emit a light like faint moon- 

 shine, which is influenced in intensity by the temperature of the mine. 

 Some mosses have been observed to be phosphorescent, especially the 

 species of the genus Schistostega, which grow in eaverns and other 

 damp places. The milky juice of Euphorbia phosphorea, a Brazilian 

 plant, becomes luminous when removed from the plants, and gently 

 heated. The leaves of Phytolacca decandra have been observed to 

 shine in the dark, sometimes with a bluish-green, sometimes with a 

 yellowish-green light. Decaying wood is well known to be often 

 phosphorescent under peculiar circumstances ; it is generally observed 

 in the wood of trees which have been buried in earth while they were 

 in a green state ; and perhaps may frequently be caused by the my- 

 celia of fungi, many of which are known to be luminous; it is removed 

 irrecoverably by drying up the damp rotten wood. Dr. Hooker, in the 

 2nd vol. of his "Himalayan Journals," p. 151, gives interesting obser- 

 vations upon this subject. At Doigiling, he says, during the damp 

 warm summer months (May to October), at elevations of 5000 to 8000 

 feet, the phenomena of phosphorescence in wood may be witnessed 

 every night by penetrating a few yards into the forest. A stack of 

 fire -wood, collected near the cottage in which he was lodged, presented 

 a beautiful spectacle for two months (in July and August) ; and on 

 passing it at night he had to quiet his pony, who was always alarmed 

 by it. The phenomenon, he continues, invariably accompanies decay, 

 and is common on oak, laurel (Tethranthera), birch, and probably other 

 timbers ; it equally appears on cut wood and on stumps, but is most 

 frequent on branches lying close to the ground in the wet forests. He 

 had reason to believe that it spreads with great rapidity from old sur- 

 faces to freshly cut ones, and did not in the least doubt that it is a vital 

 phenomenon, and due to the mycelium of a fungus, as he had observed 

 it occasionally circumscribed by those black lines which are often seen 

 to bound mycelia on dead wood, and to precede a more rapid decay. 

 He tried often, but in vain, to coax these mycelia into developing some 

 fungus by placing them in damp rooms. When camping in the moun- 

 tains he frequently caused the natives to bring phosphorescent wood 

 into his tent for the pleasure of watching its soft undulating light, 

 which appeared to pale and glow with every motion of the atmosphere ; 

 except in this difference of intensity, it presented no change in appear- 

 ance night after night. Alcohol, heat, and dryness, soon dissipated it ; 

 it had no odour, and his dog, who had a fine sense of smell, paid no at- 

 tention to it when it was laid under his nose. The statements as to 

 the luminosity of flowers are so very contradictory, that fresh observations 

 alone can procure unimpeachable evidence on the subject. The flowers 



* Henfrey, "Element. Course of Botany," p. 615. 



