[ 165 ] 

 XX. Intelligence and Miscellaneous Articles. 



ON THE CAUSE OF THE PHOSPHORESCE^CE OF THE AGARIC OP 

 THE OLIVE. BY M. FABRE. 



THE phosphorescence of living plants is a very rare phsenomenon ; 

 it has been proved principally in some species of the great class 

 of Fungi. The Agaric of the olive {Agaricus olearius) has been espe- 

 cially indicated as possessing this property ; it has been the subject 

 of the researches of Prof. Delille, and more recently of M. Tulasne ; 

 the latter, however, in his important memoir upon this subject, in- 

 dicates some gaps to be filled up, especially in regard to physico- 

 chemiccd experiments, and the positive proof of the cause of the 

 luminous phsenomenon exhibited by this Agaric. This has been the 

 object of M. Fabre's experiments. 



After ascertaining, like the observers who had preceded him, that 

 this phaenomenon occurs in the Agaric when living and perfectly 

 healthy, and more especially in the lamellae which olothe the lower 

 surface of its pileus, he proves, contrary to Delille's assertions, that 

 the phosphorescence is not intermittent, but that it continues during 

 the day as well as during the night. His experiments have also 

 given him the following results : — 



1. Exposure to the light of the sun has no sensible influence on 

 the phosphorescence of this Agaric when it is afterwards removed to a 

 dark place. 



2. The hygrometric state of the air has no influence upon the 

 phsenomenon so long as there is no desiccation of the tissues in which 

 it occurs. 



3. Heat, within certain limits, does not modify the phosphorescence, 

 but a reduction of temperature below 46° to 50° F. causes it to 

 cease, without, however, destroying the power of again producing it 

 when the temperature rises again above this limit, at least if the 

 temperature has not been long maintained between 32° and 36° F. 

 A heat above 122° F., on the contrary, completely destroys the pro- 

 pertj' of shining in the dark; and in both cases, in the author's opinion, 

 this is caused by an alteration in the tissues or fluids of the Agaric. 



4. The phosphorescence is the same in aerated water as in the 

 open air, but it diminishes by degrees if the Agaric be kept long in 

 the same water, and the presence of dissolved carbonic acid is then 

 evident. In water deprived of air by boiling, on the contrary, the 

 phsenomenon ceases in a few moments, but reappears immediately 

 on exposure to the air. 



5. The phosphorescence ceases in vacuo in hydrogen gas and car- 

 bonic acid ; it afterwards reappears in the air. A prolonged stay in 

 carbonic acid causes it to cease permanently, as also a very short 

 immersion in chlorine, which evidently produces an alteration in the 

 tissues of the Agaric. 



6. Pure oxygen does not increase the brilliancy of the light, which 

 appears to be the same in this gas, in the air, and in aerated water. 



7. When phosphorescent, the Agaric produces a quantity of car- 

 bonic acid much greater than that which it exhales, under similar 

 circumstances, after its period of ])hosphorescence has passed. On 

 the other hand, the Agaric in its phosphorescent and non-phosj)hor- 

 esccnt periods, when kept at a temperature below that necessary for 



