A SUMMARY OF BOG THEORIES 321 



sar}' for the formation of bogs it seems probable that in this 

 combination would be a good place to seek for the production 

 of the toxic substance or substances. Bauman and Gully (2) 

 have found that the acidity of peat soils is due to the fact that 

 the colloidal matter of the cell covering of the hyaline sphagnum 

 cells retains chiefly the basic ions of the dissolved salts contained 

 in the cells, the acid ions being thus freed and rendering the soil 

 water acid. It is not established, however, that acidity is the 

 cause of the toxicity. 



d. The decay of plants other than Sphagnum. This in con- 

 nection with (c) has been suggested by Dachnowski (15, p. 140 

 and 19, p. 514). 



e. The absence of any adsorbing agent such as ordinary soil. 

 This wa;^ suggested by the writer (41) since the toxicity of bog 

 water can be removed by means of adsorbing agents (Dachnow- 

 ski 15, p. 134; 16, pp. 397 and 407). The effect of adsorbing 

 agents on toxins was established by True (59, p. 15). 



HOW DO THE TOXIC SUBSTANCES IN BOG WATER ACT ON 



PLANTS? 



a. By causing a change of form of the plant. Livingston 

 (33, p. 351) found this to be true of Stigeoclonium. 



b. By causing xerophytic structures. Transeau (57, p. 867) 

 found this to be true of Rumex acetosella. 



c. By decreasing growth. Dachnowski (15, pp. 132-141 

 and 20, p. 311) found this true in his experiments on the -^rowth 

 of agricultural plants and Marchantia gemmae in bog water. 



d. By decreasing absorption. This was suggested by Schim- 

 per (52, p. 4). 



e. By decreasing transpiration. Dachnowski (15, p. 140). 



/. By decreasing absorbing surface. This seems to be estab- 

 lished, at least in some cases, by the work of the WTiter (41, p. 

 318). Dachnowski (18, p. 15) disagrees with this view. Coville 

 finds that the roots of Vaccinium corymbosum whose favorite 

 habitat is peat are entirely devoid of root hairs. 



g. By increasing absorption to such an extent that it inter- 

 feres with the efficiency of root tips as growing organs. 



