66 CHYMISTRY APPLIED TO AGRICULTURE. 



has become adapted to fruit containing kernels ; and pro- 

 duces excellent wheat, whereas before it bore only scanty 

 crops of oats and rye. 



ARTICLE 11. 



Of Stimulating Manures. 



I HAVE hitherto spoken only of those manures which 

 contain, at the same time with aliments necessary for 

 vegetation, the salts which are inseparable from them ; 

 and which pass, in a state of solution, into the organs of 

 plants to stimulate their action. I shall now speak particu- 

 larly of these salts, explaining in what manner they act, 

 and how their utility in vegetable economy differs materially 

 from that of the alimentary principles ; and showing that 

 they can often be so employed as to increase the activity of 

 vegetation. 



It appears from the results of the critical experiments 

 which M. Saussure has made upon these substances, that 

 the salts and extracts, when dissolved in water, are absorbed 

 by the roots of plants. 



The absorption of hurtful salts is easy and abundant, in 

 proportion as the plant is languishing, sickly, or mutilated. 

 From this principle, established by experiments, it follows 

 that the absorption of fluids and salts by the plants is not 

 a passive and purely physical faculty ; but one, which is 

 determined by those laws of vitality, which govern the 

 plant during life. It is only when the power of these laws 

 is weakened by a sick or languishing state of the plant, 

 that external agents can act upon it in an absolute manner. 

 Plants do not draw in indifferently, or in the same quan- 

 tities, all substances which can be held in solution by wa- 

 ter ; they absorb, from preference, those which are least 

 viscid. 



From the preceding statements it is rational to conclude, 

 that plants do not maintain a strictly passive state in regard 

 to their aliments ; but that to a certain degree they have a 

 preference, and taste, respecting them; and that the physi- 

 cal laws predominate, to the injury of the vital organization, 

 in proportion to the sickly or languishing condition of the 

 plant. 



