THE ASH OF PLANTS. 191 



essary to plant-life that the sodium which appears to 

 replace potassium is accidental, and that the replaced 

 potassium is accidental also, or in excess above what is 

 really needed by the plant, and leaves us to infer that the 

 quantity of these bodies absorbed depends to some ex- 

 tent on the composition of the soil, and is to the same 

 degree independent of the wants of vegetation. 



Alkalies in Strand and Marine Plants. The 

 above conclusions apply also to plants which most com- 

 monly grow near or in salt water. Asparagus, the beet 

 and carrot, though native to saline shores, are easily ca- 

 pable of inland cultivation, and indeed grow wild in com- 

 parative absence of sodium compounds. 



The common saltworts, Salsola, and the samphire, 

 Salicornia, are plants which, unlike those just men- 

 tioned, seldom stray inland. Gobel, who has analyzed 

 these plants as occurring on the Caspian steppes, found 

 in the soluble part of the ash of the Salsola brachiata 

 4.8 per cent of potassium oxide, and 30.3 per cent of 

 sodium oxide, and in the Salicornia herbacea 2.6 per 

 cent of potassium oxide and 36.4 per cent of sodium 

 oxide, the sodium oxide constituting in the first instance 

 no less than ^ and in the latter ^ of the entire 

 weight, not of the ash, but of the air-dry plant. Potas- 

 sium is never absent from these forms of vegetation. 

 (Agricultur-Chemie, 3te Auf. y p. 66.) 



According to Cadet (Liebig's ErndJirung der Veg., 

 p. 100), the seeds of the Salsola kali, sown in common 

 garden soil, gave a plant which contained both sodium 

 and potassium ; from the seeds of this, sown also in 

 garden soil, grew plants in which only potassium-salts 

 with traces of sodium could be found. These strand- 

 plants are occasionally found at a distance from salt- 

 shores, and their growth as strand-plants appears to be 

 due to their capacity for flourishing in spite of salt, and 

 not from their requiring it. (Hoffmann, Vs. St., XIII, 

 p. 295.) 



