( 164 ) 



Memoir on the Degree of Selection exercised by Plants, with re- 

 gard to the Earthy Constituents presented to their absorbing 

 Surfaces. By Charles Daubeny, M. D., F. R. S., L S., 

 G. S., Professor of Botany and Chemistry in the University 

 of Oxford.* 



Amongst the subjects recommended for consideration by the 

 Chemical Sub-committee of the British Association for the Ad- 

 vancement of Science, during their meeting at York in 1831 , was 

 that of the sources from which organic bodies derive their fixed 

 principles ; and as it was known to some of my friends that I 

 had been engaged in certain inquiries that bore upon this sub- 

 ject, a request that I would undertake the investigation was ac- 

 cordingly entered upon the minutes. I obtained, therefore, 

 from this circumstance an additional motive for endeavouring, 

 so far as my opportunities allowed, to prosecute the train of ex- 

 periments which I had begun ; and if I should scarcely yet 

 have succeeded in determining to my entire satisfaction, whether 

 or no there be any foundation for the idea sometimes entertain- 

 ed, that the earthy and alkaline principles which organized and 

 living bodies contain are in any case elaborated by themselves, 

 the reason must be sought for rather in the intricacy of the sub- 

 ject than in any want of disposition on my part to carry on an 

 inquiry so recommended. Incidentally, however, the results of 

 my researches seem to lead to the establishment of a fact, which, 

 as it serves to modify one of the conclusions deduced by the 

 younger Saussure from his experiments on vegetation, -J* deserves, 

 perhaps, a brief notice ; and it is on this account, rather than 

 for the sake of any new light I may have been able to throw 

 upon the principal point in question, that I am desirous of lay- 

 ing before the Society the following details. 



In the experiments that were made by Braconnot,J Schrader,§ 

 and others, with a similar intent to my own, the plants operated 

 upon, in order that all external sources for the supply of earthy 

 matter might be cut off, were made to vegetate either in washed 

 sand, in sulphur, in pounded glass, in small shot, or in certain 

 metallic oxides. It occurred to me, however, that without pla- 



* Read to the Linnean Society November 19, and December 3, 1833 ; and 

 printed for their Transactions. 

 •J- Becherches Chimiques sur la Vegetation, 1804. 



X Annates de CMmie, vol, lxi. p. 137. § Gehlen's Journal, vol. v. p. 255, 



