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Inquiry into the Changes which the Atmosphere undergoes when 

 in contact with certain Vegetables which are destitute qf green 

 leaves > Sft. By M. F. Marcet.* 



It is now a long while since, thanks to the labours of many 

 physiologists, and, in particular, to those of our countryman M. 

 Theodore de Saussure, we have been familiar with the action 

 of the atmosphere in the nutrition of vegetables, which are pos- 

 sessed of leaves and other green parts. It is known that this 

 action consists of many distinct operations, some of which tend 

 to vitiate the atmosphere, either by depriving it of its oxygen, 

 or by the formation of carbonic acid gas, whilst others, on the 

 contrary, tend to purify it by the exhalation of a considerable 

 quantity of oxygen gas. Theory, supported by experiment, 

 goes to demonstrate that the latter of these processes exceeds 

 the former, and that growing vegetables have a tendency to in- 

 crease the quantity of the oxygen of the atmosphere. Thus 

 they afford a kind of compensation for the continual absorption 

 of oxygen, which goes on in combustion, and in the respiration 

 of animals. 



But there is a numerous class of vegetables, viz. that of 

 cellular plants* which is completely devoid of green parts, and 

 whose mode of nutrition appears to be very different from that 

 of other plants ; of which series mushrooms form the most im- 

 portant example ; and every thing induces us to think that these 

 plants are not like green ones, endowed with the property of 

 decomposing carbonic acid gas through the agency of the light, 

 since many of them thrive almost in complete darkness. How, 

 then, is it that they assimilate to themselves the carbon which 

 enters into their composition ? and how is the work of nutrition 

 effected generally in this class of vegetables ? These are points 

 of which we are almost in complete ignorance ; and, therefore, 

 I have thought that some experiments regarding the action of 

 mushrooms upon the atmosphere, during the process of vegeta- 



* From a Memoir read to the Societe de Physique et cTHistoire Naturelle de 

 Geneve, on the 18th December 1834. Taken from the Memoirs of the Society, 

 torn. vii. part 1st. 



