1909] 



BURNS— BOTANICAL SURVEY OF HURON VALLEY 



447 



originally. The volume of water, however, is much smaller than it 

 appears in the figure just referred to, as is seen in a profile through 

 this section of the lake (fig. 2). The greatest accumulation of peat 

 is on the western side. The zonal arrangement is also quite different 

 on the two sides. The bog-shrub, tamarack, and maple-poplar zones 

 are almost entirely lacking on the east. On the west, all the zones are 

 present, the tamarack zone being very wide especially in the south- 

 western portion. 



F E 



D 



B 



A 



Fig. 



•First Sister Lake. Profile east and west. A open water; B bog sedge; 

 C bog shrub; D tamarack; E maple-poplar; F willow. Scale: vertical, 1:600; 



horizontal, i : 2880. 



a clearing 



In fig. 1 it is interesting to observe that the open water now lies 

 over the deepest part of the post-glacial lake; and to follow the 

 variations in the width of the tamarack zone. The southern area 

 is broken by areas of bog shrubs, showing that the tamarack has not 

 entirely captured the area. The northern group, on the other hand, 

 is disappearing, and when a number of trees were cut out for wood a 

 few years ago an entirely different society of plants came in- 

 society. In other words, conditions favoring the development of a 

 tamarack society are found where the original post-glacial lake was 

 forty feet (i2.i7 m ) or more in depth, and where the depth was less 

 than this conditions are favorable for the development of the next 

 zone of plants. 



Bog near Carpenter's Corner.— This is a small bog east of 



Ann Arbor. It is surrounded by high hills on the north, west, and 

 south. On the east a narrow ridge about five feet (1 . 5 m ) high sepa- 

 rates it from a large " drained swamp." A ditch has been dug through 



The original post-glacial lake was small, 



this ridge to drain the bog. 



