16s On the Identity of Silex and Oxygen, 



In the experiments to which I allude, the seeds were sown 

 in a variety of the most insoluble bodies, as sulphur, glass, 

 leaden shot, litharge, sand and such like matters, which 

 could not assuredly yield of themselves any nourishment, 

 but merely to serve as the supports, to which the fibres of the 

 roots might cling. In all these instances the plants grew and 

 generally seemed to thrive ; but whether they prospered in 

 the same degree as plants that are raised under common cir- 

 cumstances, I am not disposed to affirm; it is quite sufficient 

 for my purpose to find, that they yielded the same principles 

 by analysis as vegetables of the same species generally contain, 

 when cultivated in the usual way or left to nature ; and that 

 potash, silex, lime, the salts and, in short, all the products 

 peculiar to each species were obtained. There are many very 

 pertinent remarks upon this process by M. Braconnot, who 

 seems to have accomplished his object with great attention 

 and ability*. Various arguments have been offered tending 

 to invalidate the conclusions drawn from this method of ex- 

 perimentiniz; ; but, all those which I have seen, amount to a 

 mere simple denial of the facts, or to captious objections built 

 upon unfair premises. 



Contrary to a very generally adopted theory, it appears, that 

 plants, during their vegetation, do not emit oxygen or pure 

 air; that nitrogen is not necessary to their growth, though 

 they very frequently exhibit it to be in their composition; 

 that " oxygen is, by the vegetative process, converted into 

 carbonic acid without entering into the vegetable system '," 

 that neither the presence nor absence of carbonic acid causes 

 the least difference in the health and growth of ])lants ; and 

 that it is always, however, necessary that oxygen should be 

 present. It is farther remarked, " that, instead of absorb- 

 ing carbonic acid from the atmosphere, plants, by their ve- 

 getation, are constantly produciiig it;" and that, "since 

 carbonic acid is necessarily a product and consequence of 

 germination, it seems absurd to consider it at the same time 

 as an exciting principle and a cause." To these observations 

 I may add the following question, by the same intelligent 



* Ann. de Chimie, Fcv. et Mars, 1807. 



philosopher. 



