15) TRANSEAU—BOGS OF THE HURON RIVER VALLEY 367 
land through reef building. ‘These swamps have been described by 
SHALER, KEARNEY, JULIEN, and others (46, 26, 24, 7). They reach 
their greatest development in eastern Virginia, North Carolina, 
Florida, and the Mississippi floodplain. They may contain either 
silt or fresh water, and their vegetation is noted for its density and 
luxuriance. : 
The geographical distribution of peat deposits is of interest in 
this connection because it points to certain factors which contribute 
to the preservation of humus materials. Certainly in arctic latitudes: 
the most significant factor is the low temperature, for humus accu- 
mulates to great thickness even with a scant vegetation. In the 
northern states and southern provinces of Canada, peat is associ- 
ated with basins containing stagnant water or cold springs. The 
annual increment from the vegetation is greatly increased over that 
of the tundra. Mild temperatures and stagnant waters combine 
0 preserve the plant débris. When we come to the coastal plain 
ees of the southern states, this process takes place only where a 
luxuriant vegetation is combined with areas of stagnant water of 
considerable depth. 
To put it sharply, we may say that, in spite of the scant vegetation, 
the cold of the tundra results in peat accumulation. In temperate 
latitudes, mild temperatures and stagnant water combine to prevent 
. Complete disintegration of a vigorous vegetation. In the south, 
spite of the high temperature, the luxuriance of the vegetation 
and stagnant water unite to make peat formation possible. 
THE PROCESSES INVOLVED IN PEAT FORMATION. 
its nie ag any reason the living protoplasm in a plant or any of 
of Hg nS Is brought to the condition of death rigor, the pare 
and ci te for a prolonged period inaugurates certain chemica 
exc Physical processes which result in the breaking down of the 
— complex structures and compounds making up the living 
is the loss ong the first outward signs of such im. 
and in a of water. The cells of soft tissues lose their normal ne 
The any case the tissue becomes more or less filled with gases- 
Protoplasts as such disappear, and in their place granular : 
hydrate and proteid bodies are to be found. 
