1914 ] 
Jackson; Land Vertebrates of Ridgeway Bog 
9 
’in these bogs; he describes the anatomical characteristics of sev- 
eral bog plants, and hnally explains the results of experiments 
performed to answer the question of the efficiency of a cold sub- 
stratum and soil acidity to produce xerophily. ‘‘An examination 
of all the physical and chemical data now available 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 the Pleistocene times 
and has remained undisturbed, we find today the bog flora. Where 
the habitat is of recent origin or has been recently disturbed, we 
find the swamp flora, or mixtures of swamp and bog species’’ 
(Transeau, 1905-1906, p. 37). “It is shown that during the early 
stages of bog development, bog sedge, bog shrub, and conifer 
societies follow each other in the invasion of the basin. These 
several societies may vary considerably in composition, but they 
are closely related and show every gradation in a definite order 
of succession. The bog conifers, however, show no relationship 
to the surrounding broad-leaved forests of the upland. On the 
other hand, where clearing has occurred, swamp sedges, swamp 
shrubs, and swamp trees gain the ascendency, and these not only 
show an order of succession among themselves, but are genet- 
ically related to the broad-leaved trees of the region. The bog 
societies are a part of the northeastern conifer forest formation, 
while the swamp societies are related to the southeastern broad- 
leaved forests” (Transeau, 1905-1906, p. 38). 
A paper by Weld (1904) is descriptive of the vegetation of the 
first of Three Sister Lakes in southern Michigan; he describes the 
general character and physiographic features of the area studied, 
and recognizes five vegetative zones which he designates respec- 
tively from the inner zone outward as the Potamogeton zone, 
the Nuphar zone, the Carex and sphagnum zone, the Cassandra 
zone, and the forest zone. He also notes ecological succession: 
“The lake was first invaded by aquatic and amphibious plants. 
As humus accumulated, there followed in turn sedges and sphag- 
num, shrubs, a pure tamarack, and then a mixed, soft-wood, 
deciduous forest” (he., p. 52). 
One of the best contributions to our loiowledge of American 
bogs is that of Davis (1907) in which he describes in considerable 
detail the vegetation of a large number of Michigan bogs in 
