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nous both in itself and its mycelium ; he had also seen Polyporus svlfureus, lumi- 

 nous ; and he adds, that Mr. C. E. Broome had met with a luminous Corticium, 

 the name of which is not given. It would appear to be a very rare circumstance 

 to alight upon a fully developed fungus showing this property. 



3rd. — May we assume that all reputedly luminous species exhibit this 

 phenomenon at some period of their gro\vth, and if so, what are the favourable or 

 adverse conditions which affect luminosity ? 



That one often meets with the species belonging to this country without 

 observing any luminosity in them does not of itself dispose of the first part of this 

 question. The life of these plants often extends over two months or more, and 

 they require to be watched in their early development, their maturity and decay, 

 and also in the varying conditions of the atmosphere, before it can be affirmed 

 that species reputed to be luminous in particular instances never are so. When 

 we bear in mind their place of growth, in remote spots in dense woods, and that 

 the light is only visible in the night time, the difficulty of arriving at the facts 

 will be evident. M. De Candolle considered that Agarieus olearius was luminous 

 in a state of decay, while M. Tulasne, who conducted a long series of careful ob- 

 servations on this species, satisfied himself M. De Candolle was mistaken, and 

 that it was luminous only while the plant was in full vigour of growth, thus con- 

 firming the opinion of M. Delile, who also carefully studied this species, and de- 

 clared that the luminosity ceased at the moment when the fungus ceased to grow, 

 and that even while growing it did not at all times exhibit it. Mr. Worthington 

 Smith in some experiments on wood luminous from the presence of Rhizonior- 

 pha found, that after extinguishing it by three methods, viz., — saturation in oil, 

 immersion in boiling water, and freezing in solid ice, it again recovered. Tulasne 

 on the other hand found, that although he could revive specimens of Rhizomorpha 

 which had been luminous, but had been dried for a month, so that they would 

 grow, he never observed a revival of their luminosity. The most recent experi- 

 ments that I can discover are those instituted by M. Ludwig (and quoted by 

 A.B.M. in Gardeners' Chronicle, 1874, p. 361), on pine wood attacked by Rhizo- 

 morpha. He states, that raising the temperature tended to increase the lumi- 

 nosity. The upper limit he found to be 50' cent., which utterly extinguished it. 

 Fabre found the same limit in Agarieus olearius ; Tulasne found 55° cent, the 

 limits in Rhizomorpha ; Humboldt, for decayed wood 50" cent. Ludwig found 

 the lower limit to be the freezing point, while Bacon and Heinrich saw wood 

 luminous under 0'. He also found that ordinary water did not affect it, while 

 water that had been boiled and left to cool in a close vessel extinguished it in 

 20 minutes. Such are some of the variable results arrived at by different observers 

 as to the conditions affecting this property of fungi. I tried the experiment 

 of moistening in water a specimen of Agarieus Emerici, one of the most remark- 

 able of luminous species given me by Mr. Berkeley, in the hope of reviving some 

 trace of its character, but the experiment was unsuccessful. For my own part I 

 have never seen perfectly dry wood luminous, and I am disposed to think moisture 

 is an essential condition of its manifestation. It must be confessed, however, 



