480 
he toxic, as eg. was shown by van OstERHOUT’s soil-experiments. 
Addition of CaCl,-solutions to the otherwise fairly favourable soil 
was injurious to the cultivated plants; addition of KCl-solutions was 
not. Van Ostrruovr interprets this by pointing out that through the 
addition of Caleium the relation of the two metals departs more 
and more from the optimal whereas it approximates the optimal 
relation through the addition of Potassium. 
Reverting to our broom we see that relative to the soil of the 
Land van Diepenhorst the calcium-content of the soil of the Central- 
dunes rises from 0.015 °/, to 0.90°/,, i.e. + 60 times the original 
value. On the contrary there is no appreciable total increment of 
the potassium-, and the sodium-salt-content: in the Central-dunes 
this was 0.08 °/,, in the Land van Diepenhorst 0.06 °/,. 
The relation in the Western and Central-dunes has been largely 
modified, so that the equilibrium for the true calcifuge plants, such 
as Sarothamuus, has been disturbed. The view is favoured by the 
fact that calcifuge-plants, such as Castanea vesca, can be cultivated 
in caleium-rich soil, provided the soil is of itself potassium-rich *), 
or potassiuin is added to it, ScHiMPER*) maintained that calcium 
inhibited the absorption of ironsalts, and that addition of ironsalt- 
solution to calcium-rich soil removed the excited chlorosis. By others, 
among whom SIDORINK®), this was however refuted and ascribed to 
the alkalinity of the nutrient solution that had been used. 
For Magnesium Lonw‘*) asserted that a certain ratio of Ca and 
Mg is required for a satisfactory development, which, however, has 
been negatived by Russian and American writers*) on the science of 
manuring. 
With the method for soil-examination adopted by me I found in 
both soils only traces of magnesium; I, therefore, refrain from giving 
my opinion about this question, which may be solved through 
subsequent experiments, which I purpose to perform with the Saro- 
thamnus by cultivating it on caleium-richer soil to which various 
salts will be added. This however is a time-consuming undertaking ; 
for the time being experiments with water-cultures of buck-wheat 
were indicative of the great importance of the antagonism of the 
salts of univalent and bivalent metals in the problem of calcifuge plants. 
1) ARNOLD ENGLER, Ber. Schweizer. bot. Ges. 1901. 
2) ScHiMPer, Pflanzengeographie. 1908. 
3) Srporin. Ergebn. Landw. Stat. Moskou 1916.. 
4) Loew. Bull. Agric. Coll. Tokyo 1902. Die Lehre vom Kalkfactor. Berlin 1914, 
5) A. Dosarenxo Journ. f. experim. Landwirtschaft 1903, F. A. Warr Journ. 
agr. research 1916. 
