undergoes when in contact with Vegetables. 243 



There had in this experiment, then, been the absorption of 

 .29 of nitrogen, and the evolution of .58 of carbonic acid. This 

 experiment, conducted for twelve hours during the night, fur- 

 nished a result almost identical with the foregoing. 



3d Experiment. — Four mushrooms of the species Agaricus 

 amarus were introduced under a receiver enclosing 29.17 cubic 

 feet of nitrogen, the thermometer standing at 66° Fahr. At the 

 end of twelve hours the volume of gas had augmented to 30.64, 

 and was found to consist of 29.17 of nitrogen, and .87 of car- 

 bonic acid. 



In this experiment there was apparently no nitrogen absorbed, 

 and the sole effect of the mushrooms seems confined to the evo- 

 lution of .87 of carbonic acid. 



The conclusions which result from this inquiry, and to which 

 we have been conducted by the series of experiments which has 

 been detailed, may be arranged in the following order : 



1*^, Mushrooms whilst growing in atmospherical air produce 

 upon it changes very different from those which are effected by 

 green plants placed under similar circumstances. Mushrooms 

 very speedily vitiate the air, both by absorbing its oxygen, to 

 form carbonic acid gas at the expense of the carbon of the vege- 

 table, and also by the disengagement of carbonic acid gas, formed 

 on all occasions when the experiment is conducted for a sufficient 

 length of lime. 



2(i, The changes which the atmospheric air undergoes from 

 the growth of mushrooms appears to be the same both day and 

 night. 



Qd, If fresh mushrooms are placed in pure oxygen, a great 

 part of the gas disappears at the end of some hours. A portion 

 of the absorbed oxygen combines with the carbon of the plant, 

 whilst another portion appears to enter into the vegetable, and 

 to be replaced, in part at least, by the nitrogen disengaged from 

 the mushroom. 



4sth^ Fresh mushrooms, by remaining for some hours in pure 

 nitrogen, change very little the nature of this gas. The only 

 effect produced is confined to the disengagement of a small 

 quantity of carbonic acid, and in some cases to the absorption of 

 a very trifling quantity of nitrogen. 



