THE ASH OF PLANTS. 175 



substances employed. He gives as the result of numerous 

 experiments, that for wheat, oats, and barley, in the early 

 vegetative stages of growth, soda, while advantageous, 

 is not essential, but that for the perfection of fruit an ap- 

 preciable though minute quantity of this substance is in- 

 dispensable. ( Versuche und Eesultate uber die Nahrung 

 der Pflanzen, pp. 12, 27, 29, 36.) 



Stohmann's single experiment led to the similar conclu- 

 sion, that maize may dispense with soda in the earlier 

 stages of its growth, but requires it for a full development. 

 (Henneberg^s Jour, far Landwirthschaft, 1862, p. 25.) 



Knop, on the other hand, succeeded in bringing the 

 maize plant to full perfection of parts, if not of size, in a 

 solution which was intended and asserted to contain no 

 soda. ( Vs. St., Ill, p. 301.) Nobbe & Siegert came to 

 the same results in similar trials. with buckwheat. (Vs. 

 St., IV, p. 339.) 



The experiments of Knop, and of Nobbe & Siegert, 

 while they prove that much soda is not needful to maize 

 and buckwheat, do not, however, satisfactorily demon- 

 strate that a trace of soda is not necessary, because the 

 solutions in which the roots of the plants were immersed 

 stood for months in glass vessels, and could scarcely 

 fail to dissolve some soda from the glass. Again, 

 slight impurity of the substances which were employed in 

 making the solution could scarcely be avoided without 

 extraordinary precautions, and, finally, the seeds of these 

 plants might originally have contained enough soda to 

 supply this substance to the plants in appreciable quantity. 



To sum up, it appears from all the facts before us : 



1. That soda is never totally absent from plants, but 

 'that, 



2. If indispensable, but a minute amount of it is re- 

 quisite. 



3. That the foliage and succulent portions of the plant 



