Relation to Chalk and Mineral Salts. 
85 
VI. Sphagnum and Mineral Solutions. 
It remains to consider the fairly widespread opinion that the Bog-mosses 
are sensitive to high concentrations, as such, of mineral solutions. From 
experiments quoted it is clear that some salts are much more dangerous 
than others, but the effect of a complete culture solution has not been tried. 
In making up a solution, the first difficulty that meets one is the phosphate 
supply. The extreme toxicity of phosphates has been pointed out by Paul, 
and emphasized by Haglund. I tried a series of ten phosphates on .S. con- 
tor turn, and found it considerably more resistant than the species ( medium ) 
tested by Paul. It withstood at least 50 mg. of all of them. Further, the 
toxicity was considerably lessened by the presence of calcium sulphate. 
In its presence 250 mg. were resisted. In view of this experience a solution 
of the following constitution was employed : 
Calcium nitrate .... 
• 75° mg. 
Potassium nitrate 
• 5 °° mg. 
Potassium dihyd. phosphate 
• 15° mg. 
Magnesium sulphate . 
. 400 mg. 
Potassium chloride . 
. 200 mg. 
Iron sulphate .... 
. trace. 
The reaction is acid ; but a second set of cultures was tried with the 
same solution to which just sufficient sodium hydroxide had been added to 
neutralize the acid. The concentrations used and the results are given in 
Table X. 
Table X. 
Growth of Sphagnum 
contortum. 
recurvum. 
rubellum. 
Concentration. 
°/ 
acid. 
O/ 
alk. 
acid. 
alk. 
acid. 
alk. 
O/ 
% 
0*01 
/o 
118 
120 
% 
170 
142 
% 
66 
% 
63 
0-05 
138 
125 
147 
118 
76 
43 
0*1 
I 35 
95 
149 
90 
73 
20 
0-25 
112 
93 
IIO 
35 
5 i 
33 
°*5 
60 
58 
70 
49 
35 
27 
rubellum is slightly harmed by even the most dilute acid solutions, 
and can evidently not support even low salt concentrations. The other two, 
however, thrive best in stronger solutions, contortum is best in 0*05-0* 1, 
recurvum in o-oi, though it shows a vigorous growth in the next higher 
concentrations. When the solution is originally alkaline, the favourable 
concentrations are lowered in all cases. This again demonstrates very 
clearly the effect of the alkaline reaction. Although the two more resistant 
species grow well in solutions of a salt content comparable to that offered 
in water culture to flowering plants, it does not follow that these conditions 
will be equally favourable in nature. In my cultures it was seen that after 
