LUMINOSITY OF PLANTS. 389 



3. — Luminosity of Plants. 



Luminous appearances have been observed in certain plants. 

 These have been long noticed in the lower classes of plants, such as 

 Fungi. Decaying wood, in which Fungi are developed, is sometimes 

 luminous. Mr. James Drummond describes some species of Agaric, 

 near the Swan Eiver, growing on the trunks of Banksias and other 

 trees, which emitted at night a phosphorescent light sufficient to 

 enable him to read. A phosphorescent Agaric, with the upper sur- 

 face of the pileus black, while the centre and gills were white, was 

 noticed by him on the trunk of a dead Eucalyptus occidentalis. The 

 Agaricus Gardner!, found in BrazU, gives out a light of a pale greenish 

 hue, similar to that of fireflies. It is found growing on a Palm, and 

 is called Flor de Goco. Delile found luminosity in the Agaricus 

 olearius, near MontpeUier. Agaricus igneus is another luminous 

 species ; and a luminous fungus, probably a species of Didymium, has 

 been noticed on the leaves of a Spermacoce in the West Indies. Mr. 

 Worthington G. Smith mentions the occurrence of luminous fungi and 

 mycelia in the coal-mines of Glamorganshire and Carmarthenshire. 

 One of these, Polyporus armosus, gave out a phosphorescent light, which 

 was visible at twenty yards' distance. Mr. Smith also mentions Poly- 

 porus sulfureus and Corticium cceruleum, as well as a species of 

 CoUybia or Lentinus, as being luminous. In the coal-mines of Dres- 

 den certain Rhizomorphous fungi have long been celebrated for the 

 light which they emit. The spawn of the Trufile (Tuber aestivum) 

 is said to present similar appearances. The Mycelia of fungi are 

 sometimes luminous. Temperature has an influence on the intensity 

 of the phosphorescence. The luminosity increases up to 25° or 30° 

 C. ; whilst at higher temperature it decreases, and is destroyed at 50° 

 0. A low temperature stops the luminosity, the lower limit of phos- 

 phoresence being near the freezing point. A certain amount of moist- 

 ure and contact with the atmosphere are said to be essential to phos- 

 phorescence. (For notice of luminous fungi see paper by Mr. M. 0. 

 Cooke in the Gardeners' Chronicle for 1871, p. 405.) It has been said 

 that the luminosity of these fungi, as well as of decaying wood, is 

 increased by exposure to oyxgen gas. Some consider it as connected 

 with the absorption of oxygen, being in reality a slow spontaneous 

 combustion ; while, according to others, it is referable to the liberation 

 of phosphorus from some of its combinations in the plant. 



These luminous appearances are said not to be confined to fungi. 

 The younger Linnseus states that the flowers of Nasturtium, Orange 

 Lily, and African Marigold, at the end of a hot summer day give out 

 intermittent light. Mr. Dowden and Mr. James confirmed this by 

 observations on the common Marigold and Papaver pilosum; while 



