68 
Skene .— The Acidity of Sphagnum and its 
The different species are resistant to very different degrees ; the 
dwellers on the high-moor, where the supply of salts is normally very low, 
are much less resistant than those on the low moor where minerals are 
more abundant. 
Paul then extended his observations to the effects of various salts. 
All the species enumerated were tested with calcium sulphate ; an almost 
concentrated solution was employed—2 grm. per litre—and all the species 
grew satisfactorily in it. The other salts were tested with Sphagnum 
medium, a species moderately sensitive to chalk. The concentrations 
required to kill the Moss were as follows : 
Calcium nitrate, 96 6 mg. per litre. 
Potassium bicarbonate, 240; potassium carbonate, 149 ; sodium bi¬ 
carbonate, 170; sodium carbonate, 107. 
Potassium bisulphate, 720; potassium sulphate, 6,480; sodium bi¬ 
sulphate, 340 ; sodium sulphate, 5,725; magnesium sulphate, 2,500. 
Sodium chloride, about 300 ; potassium chloride, about 375 ; calcium 
chloride, 1,100. 
Dipotassium phosphate, 46; monopotassium phosphate, 36; tripo¬ 
tassium phosphate, 34-5. 
Sulphuric acid, 150; nitric acid, 82. 
Sodium hydroxide, 40. 
From this it is evident that we cannot regard Sphagnum as being 
uniformly adversely affected by the high concentrations of the mineral salts 
applied to it. Some salts it tolerates at high, others are harmful at very 
low concentrations. The salts of calcium are harmless, while phosphates 
and alkaline salts appear to be very toxic. It must further be pointed out 
that, as the salts were tried alone, the important antitoxic action of one 
salt on another which constantly takes place in nature is omitted ; this 
would probably raise considerably the concentration at which harm would 
result in a culture solution. 
Paul then goes on to discuss the relation of the harmful action of chalk 
to the ‘ acidity ’ of the Sphagnum , and here lies the greatest interest of his 
work. Before discussing it, however, it will be necessary to refer to the 
investigations of his colleagues Baumann and Gully, and of others, on the 
nature of the ‘ acidity ’ of Sphagnum and peat. 
In 1906 Count Leiningen (’ 07 ) observed that litmus paper applied to 
Sphagnum turned red, and following up this, that Sphagnum plants require 
a considerable quantity of alkali for their neutralization—10 stems 5 cm. 
long require from 1-3 to 2 c.c. of N/10 NaOH. The degree of acidity 
cannot be determined by washing out the Sphagnum and titrating the wash 
liquid, as the acid appears to be almost insoluble ; it may best be 
determined by shaking with excess of standard alkali and titrating back 
with acid. 
