Relation to Chalk and Mineral Salts. 
73 
and that the acid nature of peaty soil is probably largely due to the presence 
in it of these (mineral) acids. These compounds are already present in 
Sphagnum. The significance of these for the life of the Sphagnum is 
supposed by the authors to lie in the possibility it gives of absorbing bases 
from the very dilute solution in which the Bog-moss lives. They further 
suggest that the property is not confined to Sphagnum, but that the 
absorption of mineral salts by the root-hairs of the higher plants may take 
place in the same way. 
To return to Paul’s researches on the relation of Sphagnum to chalk. 
He suggests that the chalk saturates the acid compounds of the cell-walls, 
and so prevents the absorption of bases. This does not result directly in 
death from starvation, but it causes the plant to make an effort to replace 
the saturated compounds, with the result that metabolism is so much 
increased that death results from a sort of exhaustion. 
In support of this he brings forward the fact that different Sphagna have 
different acidities, and that hand in hand with this variation goes the variation 
in repugnance to chalk, the more acid species being also the more sensitive. 
Table IV gives the acidity of the various species in grams of acid hydrogen 
per ioo grm. Sphagnum , as determined by titration with N/4 NaOH. 
And along with these is given the quantity of calcium carbonate required to 
kill 1 grm, (dry wt.) of each species. 
Table IV. 
Sphagnum 
Acidity. 
Chalk fatal 
{in mg.). 
rubellum . . . 
0*120 
62*55 
medium .... 
0*104 
59*93 
teres . 
0*102 
172*00 
papillosum . . . 
0*101 
60 *0 2 
molluscum . . . 
0*098 
69*51 
fuscum .... 
0*096 
68*8o 
cuspidatum . . . 
0*093 
75 *i 8 
acutifolium (moor) 
0*090 
78*33 
cymbifolium . 
0*086 
125*15 
acutifolium (wood) 
0*083 
. 92*71 
contortum 
0*081 
155*25 
Girgensohnii . . 
0*079 
I2i*33 
recurvum . . . 
0*076 
126*48 
parvifolium . . . 
0*074 
i 85 H 7 
platyphyllum . 
0*060 
321*98 
The agreement between high acidity and great sensitiveness is very 
close ; only Sphagnum teres, with the high acidity of 0.102, has also a great 
power of resistance to chalk, coming in this respect third from the end of 
the list. The amounts of chalk are given, not in terms of the concentration 
employed, but as the number of mg. required to kill 1 grm. of the plant 
(dry wt.). If concentration is taken, the agreement, although it still 
holds in a general way, is not so satisfactory, as may be seen by a 
