PLANTS DISTINGUISHED BY CERTAIN SALTS. 143 



acid ; while in the case of certain plants only a third, or even 

 .ess of the residue is taken up by the acid. 



The parts of the ashes soluble in cold water consist entirely 

 of salts with alkaline bases (potash and soda). The ingre- 

 dients soluble in acids are salts of lime and magnesia ; and 

 the residue insoluble in acids consists of silica. 



These ingredients being so different in their behavior to watei 

 and to acids, afford us a means of classing the cultivated plants 

 according to their unequal quantity of these constituents. Thus 

 potash plants are those the ashes of which contain more than 

 half their weight of soluble alkaline salts ; we may designate as 

 lime plants, and as silica plants, those in which lime and silica 

 respectively predominate. The ingredients thus indicated are 

 those which form the distinguishing characteristics of the plants 

 which require an abundant supply of them for their growth. 



The potash plants include the chenopodia, arrach, worm- 

 wood, &c. ; and amongst cultivated plants, the beet, mangel- 

 wurzel, turnip, and maize. The i.imk plants comprehend the 

 lichens (containing oxalate of lime), the cactus (containing crys- 

 tallized tartrate of lime), clover, beans, peas, and tobacco. 

 Silica plants include wheat, oats, rye, and barley.* 



Salts of Potash Salts of Lime 



and Soda, and Magnesia. Silica. 



( Oatstraw with seeds (1) - - 34-00 400 02 00 



Silica I Wheat-straw (2) .... 22 00 720 0105 



Plants. 1 Barlev-straw with seeds (1) - IQ'OO 25-70 5503 



^live-straw (3) IS'65 10-52 63-89 



* The ashes of good meadow-hay (consisting of a mixture of the ashes 

 of potash, lime, and silica plants), gave in 100 parts — (Haioi.ev) : 



Silica 00- 1 



Phosphate of lime - - - - 101 



Phosphate of peroxide of iron - - 50 



Lime - - - - - - 27 



Magnesia - - - - - - 8'6 



Gypsum - - - - - -1*2 



Sulphate of potash - 2*2 



Chloride of potassium - - - 1*3 



Carbonate of soda - 2*0 



Loss 0*8 



