60 DACHNOWSKI: BOG VEGETATION AND PEAT SOILS 
ash constituents from land soils, point also to the fact that differ- 
ences in mineral components are trifling as compared with the 
biological processes in the substratum and the differences in the 
available water. 
It remains to be ascertained to what extent the absence of 
any mineral salt may lead to the unbalanced condition which 
induces the general pathological effects upon agricultural plants, 
and whether any one of the salts employed in fertilizers may in 
part or entirely counteract the injurious effects of peat and humus 
soils. Plant physiological and particularly agricultural literature 
contains numerous references to the réle of mineral salts as nutri- 
ments. It must be candidly admitted, that the effects of the 
various mineral salts produced upon the plant or the cell are far 
more easily formulated than proved and that a satisfactory inter- 
pretation is not possible as yet. It is now known that in the prepa- 
ration of mineral solutions for plants a certain ratio of the different 
salts is required. It would be of special interest to note in some 
detail the relation of potassium and calcium compounds, and the 
suitable concentrations required to counteract the toxicity of the 
deleterious bodies in peat soils. The fact that water and salts 
are as a general rule taken up in a different ratio, differing also 
according to the species of plants used as an indicator, shows that 
the relation in balanced solutions affects and is determined pri- 
marily by the diosmotic properties of the protoplasmic membrane 
and its accommodatory processes. The direct effect of mineral 
salts on the protoplasmic membrane is undoubtedly of greater 
importance than their supposedly special nutrient value. Toler- 
ance and resistance of plants to physiologically deleterious sub- 
stances, it may be added, is not one of osmotic relations to bog 
water, nor is the absorption of water a function of it. A study of 
the magnitude of the internal osmotic pressure occurring in the 
roots and in the foliage of bog plants as related to bog conditions 
has not been carried very far as yet. Wheat plants growing in 
bog soils do not, however, show more than the usual pressure* 
isotonic with a 0.3 normal solution of potassium nitrate. 
Elsewhere (Bot. Gaz. 49: 325-339. 1910; and 52: 1-33. 1911) 
the writer has shown that contrary to the position taken by 
* Fitting, H. Die Wasserversorgung und die osmotischen Druckverhiiltnisse 
der Wistenptensen: Zeits. Bot. 3: 209-275. I9QI1I. 
