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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 .ooors 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- 
