164 
ARE SOILS ENRICHED, IMPOVERISHED, [Part in. 
by man,—not their having deposited a suicidal 
poison from their roots, and thus forming cases 
of vegetable u felo de se.” 
The organs of absorption of the roots of 
wheat, beans, potatoes, turnips, or mangel wur* 
zel, cabbage, and lucern sainfoin, or the common 
grasses, probably differ as much as the internal 
and external structure of the roots and plants ; 
and, besides, searching for their inorganic con¬ 
stituents at different levels in the soil, they may 
probably be only capable of taking up those 
adapted to their peculiar constitution.* 
That the proper juices, the various peculiar 
acids, and the organic salts, found as carbonates 
in the ashes of plants, and formed by the com¬ 
bination of the alkaline bases, potash, soda, lime, 
magnesia, with the peculiar organic acids of 
plants, play an essential part in the functions 
and development of the different parts of plants, 
cannot be doubted, though we are quite in the 
dark about it. And as regards the peculiar in- 
* We don’t know whether roots have the power of selec¬ 
tion or not, and, in reference to this all-important first prin¬ 
ciple of vegetable physiology, Liebig flatly contradicts him¬ 
self. Page 92., he writes, “ All substances in solution in a 
soil are absorbed by the roots of plants, exactly as a sponge 
imbibes a liquid and all that it contains without selection.” 
Page 101., he writes, “When roots find their more appro¬ 
priate base in sufficient quantity, they will take up less of 
another.” 
