M. Marcel on the Changes of the Atmosphere, ^c. 283 

 tion, was likely to throw some light upon the manner in which 

 these singular vegetables are nourished. 



I had occasion, in 1827, to study the effects which mushrooms 

 produced on water when placed in that hquid. The conclusions 

 at which I then arrived, and which in a great measure coincided 

 with the experiments conducted at the same period by M. Th. 

 de Saussure, (communicated by him to this Society, but never 

 published), appeared in the 40th volume of the " Annales de 

 Chimier They go to show that mushrooms placed under wa- 

 ter, in all cases disengage a gas composed of hydrogen and ni- 

 trogen, the proportions of which vary according to the period of 

 examination. Some individuals have appeared to think that the 

 disengagement of the gas was nothing more than the commence- 

 ment of decomposition in the vegetable ; but the fact that the 

 one (Sphoeria digitata) which I found to disengage the most is 

 peculiarly tough in its nature, and consequently little liable to 

 decomposition, especially at the end of a few hours, appears to 

 me to meet and overturn this objection. Besides the difference 

 in the quantity of the disengaged gas, according to the quantity 

 of light to which the mushrooms were exposed, appears an ad- 

 ditional reason for attributing the evolution of hydrogen and 

 nitrogen to a vital action, and not to the decomposition of the 

 vegetable. 



It was only during the last summer that I resumed the in- 

 vestigation, the first part of which was communicated some years 

 ago to the Society. In the interval, I had always hoped that 

 the examination of the point would be again undertaken by my 

 learned colleague, whom I have already named, and who would 

 certainly have arrived at much more precise and satisfactory re- 

 sults than those which I have obtained. At the same time, the 

 long mterval of seven years having elapsed, there seems no 

 ground to hope that he will farther prosecute it, and I have 

 therefore, thought it right to delay the investigation no longer' 

 I have entered into this explanation, for the sake of reminding 

 the Society that M. de Saussure had engaged in the investiga 

 tion at the same time with myself; and so it may happen, that 

 among the experiments which I am about to detail, there possi- 

 bly may be some which have been already made by him, but the 



