OF PLANTS. 253 



lime and magnesia salts, we cannot be surprised if we do 

 not meet with them on pure sandy soils containing scarcely 

 a trace of lime ; but it would be drawing a false conclusion 

 from this, to say that the Muschelkalk, or the Keuper-lime- 

 stones, or the Jura-limestone, or any other calcareous 

 stratum of any given formation, is exactly the proper soil for 

 these plants. That a plant like the great Sugar- tangle,* 

 which is so rich in soda, iodine, and bromine, occurs only 

 in the sea, and not in fresh water, where soda is very 

 sparingly, and iodine and bromine not at all present, is cer- 

 tainly easily conceivable. But it is certain, at the same time, 

 when we decide upon the soils on a large scale according 

 to geognostic principles, that there are very few plants 

 characteristic of particular constituents, and this relation 

 is, indeed, neither very natural nor necessary. In the next 

 place, it may be asserted that all plants contain the same 

 constituents in their ashes, but in very different proportions. 

 On a soil, therefore, composed purely of one kind of earth, 

 for instance, lime, silex or gypsum, no plant at all could 

 flourish. Every soil which bears plants contains also in its 

 composition all the substances required by all plants, only 

 the proportions differ, and the predominance of silex, lime, 

 or common salt, must consequently favour especially the 

 growth of Grasses, Pulses, or Shore-plants, although these 

 are by no means exclusively confined to the proper sandy 

 or calcareous soils, or to the sea- side. In reference to this 

 point, I know really no other plants than the carbonate of 

 lime plants, the gypsum and salt plants, which I could 

 bring forward in evidence. 



In addition to the chemical conditions, there is yet 

 another, which modifies the former and, where it brings 



* Laminaria saccharina. 



