1906] TRANSEAU BOGS OF THE HURON RIVER VALLEY 37 



areas have a very different soil solution from that of the mineral 

 soils adjoining. The high water capacity of peat is detrimental to 

 plants, in so far as it prevents proper aeration of the substratum. 

 Bog waters have no higher osmotic pressure than ordinary soil 

 waters. 



The absence of sphagnum from local bogs cannot be explained 

 by the presence of calcium salts, as shown by observation, chemical 

 analyses, and experiments. ^ 



The acidity of local bog water varies from .00015 to -00258 

 normal acid. The lowest values are found in areas covered by bog 

 sedges and swamp plants, and they are approximately the same. 

 The highest occur under the tamaracks. The variations in acidity 

 are related inversely to the temperature. As shown by experiment, 

 this is because of increased oxidation at the higher temperatures. 

 It is suggested that we should find increased acidity as we go north. 

 There is no apparent relation between color and acidity, except that 

 light colored waters usually show slight acidity. The acid nature 

 of the soil solution is a factor in the competition between different 

 species for the occupancy of bog areas. 



Bog soils are notably deficient in potassium and available nitrogen. 

 Nitrifying bacteria are prevented from carrying on their normal activ- 

 ities by the acidity of the soil solution, by the lack of oxygen, and by 

 the lower temperature of the substratum. 



With few exceptions bog plants are light-demanding forms ; hence, 

 in their competition with one another, size and shading ability 

 are prime factors. 



That the conditions in the Huron valley are at present not as favor- 

 able to the bog plants as to the swamp plants, is shown wherever the 

 two societies come into competition. This fact must be contrasted with 

 the situation in the optimum region of the distribution of bog plants, 

 where the opposite relation has been shown to exist. 



An examination of all the physical and chemical data now avail- 

 able fails to account for the differences in flora of bog and swamp 

 areas in this region. The most important factor is believed to be 

 their physiographic history. Where the habitat dates back to Pleis- 

 tocene times and has remained undisturbed, we find today the bog 

 flora. Where the habitat is of recent origin or has been recently dis- 



