LUMINOSITY OF FUNGI, ETC. 



407 



morphs,' the mycelium of a tree-killing Agaric {Agan'tus vielleus) has been longest 

 known. Tulasne mentions, as. examples of spontaneously luminous Fungi, Agaricus 

 igncus from Amboyna, A. noctilucens from Manilla, and A. Gardneri from Brazil. The 

 best investigation of the spontaneous luminosity of such Fungi was supplied in 1855 

 by Fabre in the case of Agaricus olearius. This golden yellow Fungus grows 

 throughout Provence at the foot of olive trees in October and November. Accord- 

 ing to Delile and Fabre only its hymenium is luminous, and not the white spores. 

 According to Tulasne the stem also, at least here and there, is in many cases 

 luminous ; and even the interior of the Fungus is said to develope light, according 

 to him. Fabre, who made his observations at a lower temperature of the air, 

 could not detect this. The observers mentioned, however, agree that the Fungus is 

 only luminous during its period of vegetation, and that the phenomenon ceases at 

 death. Even very young specimens are actively luminous, and they retain this 

 property so long as they live. Fabre describes the light as steady, white and 

 homogeneous, resembling that of phosphorus dissolved in oil. His observations 

 were made in November, at io°-i2°C. ; and he first established that the Fungus 

 is luminous during the day as well as at night, as had already been shown by 

 Schmitz to be the case in the Rhizomorphae. A previous exposure to sunlight has 

 no noticeable influence on the subsequent luminosity in the dark, and the degree 

 of moisture of the air likewise seems to have no perceptible effect. The Fungus is 

 luminous in rainy weather and in dry, and is just as luminous in air saturated with 

 vapour. If it is dried to such an extent that death ensues, however, the luminosity 

 ceases. In the case of the Rhizomorphs, according to Tulasne, this takes place 

 sooner. At temperatures lower than + 4° or + 3° C. the phosphorescence is very 

 quickly lost, but returns again when the temperature of the air rises. The maximum 

 of luminosity is reached at 8°-io° C, and is not increased by further heating. If 

 plunged into warm water, the Fungus retains its luminosity; but as soon as the 

 temperature rises to 50° C, the luminosity disappears for ever, the Fungus being 

 then killed. 



In water containing air the phosphorescence is as pronounced as in the air ; 

 but if a luminous Fungus is plunged into boiled water, the luminosity ceases almost 

 instantaneously, returning, however, when the Fungus is withdrawn and brought into 

 the air. The phosphorescence is immediately and completely extinguished in a 

 vacuum, in hydrogen gas, and in carbon dioxide. After remaining for several hours 

 in a vacuum or in these gases, the Fungus at once regains its light on being again 

 brought into the air : a longer stay in carbon dioxide injures it however. In pure 

 oxygen the light does not become more pronounced : on the contrary, it is enfeebled 

 after thirty-six hours in this gas. The most important fact discovered by Fabre is 

 that Agaricus olearius in its phosphorescent condition forms much more carbon 

 dioxide than when it is not luminous. The pileus with its lamellae in pure oxygen at 

 i2°C. yielded, in thirty-six hours, 4-41 c.cm. of carbon dioxide for each gram of its 

 weight : a gram of non-luminous substance only yielded 2-88 c.cm. of carboa 

 dioxide. On the other hand, on treating a luminous piece of Fungus in the same 

 way at a lower temperature, where the luminosity ceased, this yielded in forty- 

 four hours for each gram of its substance, only 2"64 c.cm. of carbon dioxide; and 

 another piece, not luminous at all, 2*57 c.cm. Hence the substance capable of 



