44 8 BOTANICAL GAZETTE [jun 



occupying about one-tenth of an acre (400^ m ). It had only one [ 

 basin whose greatest depth was fifty-nine feet (i8 m ). This point was 

 considerably west of the center. The slope of the shore from the 

 eastern margin was very gradual for a distance of nearly one-third 

 the east-and-west diameter, when it becomes very steep. The eastern 

 third of the lake was about fifteen feet (4 . 57 m ) deep. The slope from 

 the western shore was much steeper, and hence the greatest amount 

 of water was west of the center. 



Today the open water has entirely disappeared. From the banks 

 a group of tamaracks may be seen. These are arranged around a 

 small central area within which are found (7) a few individuals 

 of the bog-sedge and bog-shrub zones which formerly occupied large 

 areas. Some of the plants found were Car ex filiformis, Sphagnum 

 sp., Sarracenia purpurea, Cypripedium acaule, and V actinium 

 Oxycoccus. Outside of this area is a zone of mixed vegetation. The 

 width varies from several rods to a few feet, the widest area being 

 found on the east. The dominant trees are Acer rubrum and Populus 

 tremuloides. This area has a rather indiscriminate mixture of bog 



■ 



and lowland plants — it is a tension zone in which conditions are not 

 especially favorable to either group of plants. Around this area and 

 following the shore, is found the marginal area so common to bogs. 



The plants occupying this area are those usually found in low wet 

 places along rivers. 



A comparison of this distribution with borings shows that the 

 central area is over the deepest part of the post-glacial lake. The 

 greatest surface accumulation is on the western side where the lake 

 was comparatively shallow, and over this area Acer rubrum and 

 Populus tremuloides are the dominant trees. 



It is thus possible to tell, with considerable accuracy, the depth 

 of the bottom of post-glacial lakes with one basin by the distribu- 

 tion of the present vegetation. The order of succession is lily, D0 » 

 sedge, bog shrub, tamarack, and maple-poplar. An island of Cassan- 

 dra located in a zone of Carex filiformis indicates a shallow bottom 

 (3), but when it is found in a zone of tamaracks it indicates a deep 



- 



basin. 



Dead Lake.*— This lake is located about ten miles (i6 km ) north 



3 Mr. Forest B. H. Brown assisted in making the borings. 



*# 



