SCIENTIFIC CONGRESS OF CARLSRUHE. 369 



In his memoir of 1854, M. Schroeder, had explained the preserva- 

 tive action exerted by filtering through cotton by supposing that this 

 process eliminates from the air the spores of infusoria, or the crypto- 

 gamic germs originally suspended therein, and which being deposited 

 on the fermentable or putrefiable matter, are developed at the expense 

 of that matter, and give rise to the different products which result 

 from the phenomena of fermentation and putrefaction. 



If the experiment' with the sulphate of soda seems to establish a 

 relation between crystallization and that other species of molecular 

 movement called fermentation, it tends to prove, also, that these phe- 

 nomena may take place without the concurrence of the spores of infu- 

 soria or of cryptogams suspended in air not filtered. The question, 

 apparently disposed of by the former series of M. Schroeder's investi- 

 gations, is placed on a new footing, and no longer menaces either the 

 mechanical theory of M. Liebig, nor that which results from the last 

 researches of M. Pasteur on the manner of producing and propagating 

 fermentation. 



We cannot leave the subject of chemistry without speaking of a 

 discourse by M. Liebig in the Section of botany, on the nutrition of 

 plants, and the function in regard thereto, of arable land. Till the 

 present time it has been considered that in order for mineral substances 

 to penetrate within a plant, it was necessary that they should be in a 

 state of solution. The water of rain, pure or combined with carbonic 

 acid, would thus be the dissolvent, and the liquid would be absorbed 

 by the roots. 



Establishing himself on the facts ascertained by M. Way in relation 

 to the disinfecting action exerted by arable land upon the water of 

 purin, M. Liebig shows that this absorbent action is exercised, in 

 general, upon the saline substances susceptible of serving for aliment 

 to vegetables, and that the absorption is so much the more energetic 

 as the mineral principle is more nutritious for the plant ; arable land, 

 for instance, taking up potash more rapidly than soda, conformably 

 with the fact observed by MM. Molaguti and Durocher, that vegeta- 

 bles have much more tendency to absorb the former than the latter, 

 and that certain maritime plants (the eryngium maritimum, among 

 others) contain nearly three times more of potash than of soda. 



But if the potash, the ammonia, and even the soda, are fixed by 

 arable land, the acids with which they are combined are not absorbed, 

 except in so far as they are susceptible of being useful to the vegetable. 



Water the ground with a solution of chloruret of potash or sulphate 

 of ammonia, and then examine the liquid which passes off by way of 

 filtration — that is to say, the water of drainage — the potash and am- 

 monia will have disappeared; the acids, on the other hand, will be 

 found almost entirely present. Irrigate with water containing phos- 

 phate of lime dissolved by means of carbonic acid, you will find in the 

 drainage water, the lime which existed in the water used ; but .you will 

 not find phosphoric acid ; that acid will have disappeared, having been 

 fixed in some manner by the arable land. 



It is not, then, in the saline solutions that the roots of plants take 

 up the principles which they require ; nor is it within the structure of 



24 



