THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 

 JUNE 184-6. 



LXX. Researches on the Functions of Plants, with a view of 

 showing that they obey the Physical Laws of Diffusion in the 

 Absorption and Evolution of Gases by their Leaves and 

 Hoots. By D. P. Gardner, M.D., Member of the Lyceum 

 of Natural History, fyc. * 



1. ][ CONCEIVE a plant to be a porous system, contain- 



-*• ing an internal mixture of gases, or plant atmosphere, 

 and lying in contact with common air on the one side, and 

 with the gases dissolved in the fluid of the soil on the other. 

 My object in the following remarks is to show that the plant 

 atmosphere is of a fluctuating nature, and depends on the 

 chemical action taking place ; and that whatever gases are 

 absorbed or evolved by leaves or roots, depend upon the nature 

 of the internal atmosphere at the time. To place the evidence 

 of these conclusions before the reader, I propose to examine 

 the subject under five heads : — 



1st. The epidermis or bounding membrane of plants is po- 

 rous. 



2nd. The constitution of the internal gas of plants. 



3rd. The action of roots on the gases of the soil-fluid. 



4th. The absorption of gases by plants is a consequence of 

 their porosity. 



5th. The action of plants on artificial atmospheres. 



I. The Epidermis or Bounding Membrane of Plants is Porous. 



2. The object in this place is to show, that the epidermis is 

 not merely capable of transmitting particular gases, but that 

 it obeys all the laws of a porous system. If this be found true 

 for the bounding membrane, it will necessarily be true for the 

 internal cellular structure. 



* Communicated by the Author. 



Phil. Mag. S. 3. Vol. 28. No. 189. June 1846. 2 G 



