*06 FORESl'KY OF 



inorganic constituents out of the air and distilled water J 

 and there were superficial experiments which seemed to 

 countenance the idea. Subsequently the error lay in the 

 other extreme, for there was manifested a disposition to 

 ascribe a peculiar flora to each geognostic formation. 



'The truth seems to lie between the two extremes. 

 When we find that the ashes of tobacco, of clover, of lucerne, 

 contain more than 20 per cent, of 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 musselkalk, or the keuper limestone, 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 (Laminaria 

 saccharina), 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 certainly 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 neces- 

 sary. 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 e.g., lime, silex, or gypsum no plant at all could 

 flourish. Every soil that 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 other plants, although th'ese 

 are by no means exclusively confined to the proper sandy 

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

 point/ says Schleiden, 'I know really no other plants than 

 the carbonate of lime plants, the gypsum and salt plants, 

 which I could bring forward in evidence. 



