EXTRACTS — -FOREIGN AND DOMESTIC. 337 



Wiegmann and Polstorf demonstrated the accuracy of the theo- 

 retical opinions relative to the cause of the sterility of ihis sand. 

 They took the same sand, and prepared with it, by the addition 

 of salts obtained in a purely artificial manner in a laboratory, a 

 soil likewise artificial ; they sowed in it the same plants, and found 

 them to thrive in it very well. The tobacco shot forth a stem 

 more than a metre in height, and many leaves j it flowered on the 

 25th June, produced seeds about the 10th August, and on the 8th 

 September ripe capsules were collected with perfectly developed 

 seeds. 



Barley, oats, buck-wheat, and clover were developed in a per- 

 fectly similar manner : they all came up well ; they flowered and 

 produced ripe and perfect seeds. 



It is quite certain that the fine vegetation of these plants in this 

 sand, previously quite barren, depended on the salts added. This 

 artificial soil owed its equal fertility for all these plants to the ad- 

 dition of certain substances whose presence might be demonstrated 

 in the perfectly developed plant, in the stem, leaves and seeds, and 

 whose existence in the soil and in the vegetables, puts beyond 

 doubt their necessity for the life of the plant. 

 I We can, therefore, give the most barren soil the greatest fer- 

 'tility for every kind of plants, by furnishing to it the principles 

 which are necessary for their development. In fact, to endeavor 

 to render fertile, according to these principles, a completely barren 

 'sand, requires neither trouble nor expense ; but by applying them 

 to our ordinary lands of culture, which already contain in them- 

 selves a great number of these substances, it is sufficient to furnish 

 those which are wanting, to increase those which are found in them 

 in too small quantity, and to give to the soil, by the art of agri- 

 . bulture, the physical properties which render it permeable to the 

 humidity of the air, and permit plants to appropriate these prin- 

 ciples of the soil. 



Diff'erent kinds of plants require for their vegetation and com- 

 plete development, the same inorganic aliments, but in unequal 

 quantity or unequal times ; or else they require different mineral 

 substances. It is to the difference of the aliments necessary to 

 their development, which the soil presents, that it must be attri- 

 outed, if certain kinds of plants, growing side by side, are mutu- 

 illy arrested in their development ; and if others, on the contrary, 

 |n the same condition, present a rich vegetation. 

 ' If, indeed, we compare the principles of the ash of the same 

 ^lant which is developed, in different soils, we find only very 

 slight differences in its composition. We have, as an invariable 

 jrinciple, in the straw of the graminacse, silicic acid and potassa, 

 md in their seed phosphates of potassa and magnesia ; in the 

 straw of peas, and in clover, an abundant quantity of lime is 



