478 
erows'), this constitutes a striking contrast with the Trifolium pra- 
tense occurring in the Central dunes, which has a calcium-content 
of 2.5°/, of the dry weight, i.e. 50 times the value found for Saro- 
thamnus. Next I wish to call attention to the fact that in many 
cases CaCO, exerts a noxious influence on the calcifuge plants, e.g. 
the Castanea vesca. This is a familiar fact with respect to peat-moor 
plants, to such mycotrophes as Calluna and Erica, and is perhaps 
owing to the influence of calcium-salts on the mycorrhiza. Since 
our knowledge of the entire metabolism of these mycotrophes is still 
insufficient, I prefer to leave it out of consideration here and will 
discuss the deleterious effect on Sarothamnus*). Experiments by 
Massart (l.c.) undertaken at Coxyde showed the noxiousness of the 
calcium-rich soil of the recent dunes to this plant, but the nature 
of the bad effect could not be well made out. For Sphagnum spec, 
the case is better. Experiments by Paur*) evidenced that solutions 
of as little as 0.01—-0.03°/, CaCO, are deleterious to these plants, 
which are much less sensitive to CaSO,-solutions. In that case it 
can hardly be supposed that the noxious influence of the Ca-ions, 
as such, play the principal part. *) 
This leads us -gradatim to consideration of the reaction of the 
nutrient-medium, which in the latter two cases differs with an 
addition of CaCO, or of CaSQO,. 
When 150 germs of dry sandy soil was shaken up with 50 ec. 
of distilled water and the fluid was filtered off after 24 hrs., the 
filtrate presented, in the case of the sandy soil of the sea-dunes 
(caleium-content 2 or 3°/,) a distinct alkaline reaction with lacmoid-, 
and rosolic acid solution, also a weaker alkaline reaction in the case 
of the soil of the Central- and the western dunes (calcium-content 
0,1—1,0°/). On the contrary tbe reaction was neutral or faintly 
acid in samples of sand from the “Oude Land van Diepenhorst” (cal- 
cium-content 0,01—0,02 °/,), where Sarothammus, Calluna and Erica 
occur. Would it then be possible perhaps to find a clue to the problem 
in this direction? Pavr (le) carried out an inquiry into the occur- 
rence of Sphagnum in the peat-moors of Bavaria, which also pointed 
in this direction; some cases of plant-diseases did so too *). At any 
1) In weak specimens of the calcifuge Castanea vesca, grown on a soil richer 
in calcium, a higher calcium-content is found than in the healthy specimens of a 
calcium-poor soil. 
2) Influence of the calcium-richer soil on the root-tubercles, in other words on 
the N-intake is not likely. On the calcium-richer soil the other Papilionacea, also 
have tubercles; likewise there is N-manuring by the grazing cattle in both cases. 
3) Paur, Mitt, kgf. bayr. Moorkulturanstalt, 1908. 
4) The mostly calcifuge lupin is sensitive to CaSQ,. 
5) e.g. the oat-disease of the “Veenkolonie” and the Hooghalen-disease of rye. 
