479 
rate it is evident that a difference in reaction of the groundwater 
yields quite another nutrient medium; by more calcium the decom- 
posing effect of the acids is abolished. As is obvious, it is the roots 
that undergo the deleterious influence of additional calcium, which 
is proved by the fact that the Castanea vesca, when grafted upon 
the oak, also thrives in calcium-richer soils. 
However, although this influence of the reaction of the ground- 
water is of great moment, it cannot be the only causative factor. 
This is supported by the cases in which two kinds of soil exhibit 
a similar reaction, and nevertheless possess distinctly differing vege- 
tation with identical physical factors but non-identical calcium-content. 
Cases in point are. the inland-dunes, such as the Central-dunes of 
Goeree on the one side and the sea-dunes on the other. In Goeree 
Orchis morio, Seleranthus perennis and others shun the seadunes 
(calcium-content from 2 to 3°/,). They are however indigenous to 
the Central-dunes (calcium-content 0,1—1 °/,). It is also supported 
by the fact that lupin, which is mostly calcifuge, undergoes the 
noxious influence of CaSO,-manure. In conclusion I, therefore, 
point to the antagonism of the bivalent Ca-ions and the univalent 
Potassium-, and Sodium-ions. Zoological researches by Lop’) and 
afterwards botanical experiments by van OsrTERHOUT*®) (e.g. with 
plantroots) have shown that the salts of the univalent as well as 
those of the bivalent metals, taken separately, have a toxic effect, 
which, however, is neutralised by a definite concentration of the 
others. 
Their effect on the permeability of the protoplasm is such that in 
Na-salts the permeability increases till death approaches; that in Ca-salts 
alone it first decreases in order to increase again after a certain 
minimum has been reached, till ultimately death sets in also, and 
permeability is constant, exosmosis complete *). On the other hand 
solutions of Na-, and Ca-salts in a certain ratio (e.g. 95,24 NaCl 
and 4,76 CaCl,) in experiments with Laminaria‘) do not affect the 
normal permeability at all, and render normal growth possible, which 
led van Ostpruovt (Le.) to hypothetical speculations about the action 
on the protoplasm, which cannot be gone into here. 
It is a fact, however, that excess of either salt (in casu Ca) can 
1) LoeB, Am. Journ. Physiology. Vol. 3. 1900. 
2) W. J. v. OsteRHOUT, Jahrb. f. Wiss. Botanik Bd. XLVI, 1908, On the 
importance of physiologically balanced solutions for plants. Botan. Gazette 44. 1907. 
3) TH. Weevers, Betrachtungen und Untersuchungen über die Nekrobiose und 
die letale Chloroformeinwirkung. Rec. des trav. bot. néerl. Vol. IX. 1912. 
4) W.J. v. OsrerHour, Antagonism and Permeability. Science Vol. XLV. 1917. 
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