PHYTOCHEMY. 



from the soil in the state in which it is known to us, but is 

 prepared, by the organizing powers, from original materials, 

 the nature of which we only conjecture, but cannot state with 

 certainty. As ammonia is undeniably composed of azote and 

 hydrogen, and is found especially in gluten and albumen, we 

 may, without incurring the reproach of being hasty in our 

 conclusions, assume the same ingredients for potassa and soda, 

 only in quite different proportions, and probably with a cer- 

 tain share of oxygen, by which they are put in the state of 

 oxydes. The latter substance, soda, is either drawn by 

 plants from the soil, or it is first decomposed by them into its 

 constituent parts, and with these the plants form salts similar 

 to those which are found in the soil, (343.) 



The increase of the quantity of potash in woods which 

 have been subjected to putrefaction, and which was observed 

 by Schreber, Wiegleb, and John, (John, Uber die Ernah- 

 rung der Pflantzen, s. 156. 157.), favours the opinion, that 

 alkalies are produced by the disengagement of hydrogen and 

 azote. 



359. 



We must form the same opinion respecting the earths which 

 plants contain. Lime is found not only in the ashes of plants, 

 but in albumen and in gum : it cannot, however, be derived 

 from the soil, because, as we remarked formerly (343.), it is 

 found even in those plants which have grown in pure sand, or 

 amidst granite, or which have been reared in porcelain ves- 

 sels, and nourished only by carbonic acid water. If we should 

 suppose, that still the pure carbonic acid water might contain 

 dissolved lime, this is merely a supposition, which rests on no 

 foundation of proof. 



Nor is the production of siliceous matter in plants more 

 easily accounted for. This substance is not only found in 

 considerable quantity in the larger Grasses, which grow in 

 boggy places, {Arundo phragmites, Poa aquatica, Festtwa 

 Jluitans), it forms also the chief constituent of the saccharine 

 matter which exudes from the joints of the Bamboo. But 

 this siliceous matter cannot come from tlie soil, because it 



