THE ASH OF PLANTS. 175 
substances employed. He gives as the result of numerous 
experiments, that for wheat, oats, and barley, 7m the early 
vegetative stages of growth, soda, while advantageous, 
ws not essential, but that for the perfection of fruit an ap- 
preciable though minute quantity of this substance is in- 
dispensable. (Versuche und Resultate tiber 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. fir 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. S¢., III, 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 sodais 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 te 
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 éotally absent from plants, but 
that, 
2. If indispensable, but a minute amount of it 1s re 
quisite 
%. That the foliage and succulent portions of the plant 
