Hesearches on Vegetation, 315 



Plants made to vegetate in water and in a confined atmo- 

 sphere, give only the same quantity of ashes which would 

 have been obtained from their seeds ; but in the open air 

 they acquire a small quantity, which must proceed from the 

 bodies floating in the atmosphere. 



Ashes are composed of saline parts soluble in water and 

 of pans insoluble : the proportions of the insoluble and so- 

 luble part vary according to the soil, according to the cir- 

 cumstances of vegetation, and in the different parts of a 

 plant : ashes are more abundant as the vegetable substance 

 is more distant, from the ligneous stale; but thev contain 

 the more soluble substance as thev iiave been less subjected 

 to the dissolvmg action of the water ; so that a vegetable 

 abandons the soluble salts it contains wlien exposed to the 

 action of foreign water : I regret that the author did not 

 examine the salts which the water may in this manner take 

 from vegetable substances, in order to ascertain in what 

 state of combination is the potash which becomes free during 

 incineration. 



The author found phosphates in all the vegetables the 

 ashes of which he examined : the phosphate of lime forms 

 often the greater part of the insoluble portion ; but that 

 "which is soluble contains sometimes phosphate of potash, or 

 a triple combination of phosphoric acid, potash, and lime : 

 on this occasion he examines that triple combination, wliich 

 may difier by its proportions and by the effects which che- 

 mical re-agents produce in it : ashes contain scarcely anv 

 magnesia and alumine. These results, with which several 

 others are connected, are established bv seventy-nine ex- 

 periments on incineration, to each of wfiich is added a cor- 

 responding analysis. Tlie methods of analysis followed 

 are carefully described. 



I have been able to give only a short view of this 

 iiTimense labour^ which must add to the celebrity of the 

 author. 



LVI. Memoir 



