Mr, F. F. Blackmail. Experimental Researches [Dec. 6, 



December 6, 1894. 

 The LORD KELVIN, D.C.L., LL.D., President, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The President announced that he had appointed as Vice-Presi- 



dents 



The Treasurer. 



Sir John Kirk. 



Professor J. B. Sanderson. 



Professor T. E. Thorpe. 



The following Papers were read : 



I. " Experimental Researches on Vegetable Assimilation and 

 Respiration. No. I. On a New Method for Investigating 

 the Carbonic Acid Exchanges of Plants." By F. F. 

 BLACKMAN, B.Sc., B.A., St. John's College, Demonstrator 

 of Botany in the University of Cambridge. Communicated 

 by FRANCIS DARWIN, F.R.S. Received November 15, 1894. 



(Abstract.) 



All the processes hitherto available for the estimation of carbon 

 dioxide in its biological relations are open to serious objections, 

 either on the score of the amount of time involved in their perform- 

 ance, or of their inadaptability to the estimation of small quantities 

 of carbon dioxide when slowly evolved. 



The present communication describes an apparatus in which, as a 

 result of two years' work, I have succeeded in combining a high 

 degree of chemical accuracy with special adaptability to biological 

 research. 



Thus by its aid the evolution of C0 2 , by a single germinating seed 

 or by a small area of a foliage leaf, can be accurately estimated from 

 hour to hour without a break, for any desired time, while for the same 

 area of leaf, the more active absorption of C0 2 in assimilation can be 

 easily determined for such short periods of time as fifteen minutes, 

 and that at the same time separately for the two surfaces of one and 

 the same leaf area. Further, for the purposes of this assimilation, 

 a current of air containing any desired proportion of C0 2 , however 

 small, can be supplied continue iisly to the tissue under investigation, 



