128 



SEVENTH REPORT. 



which the ground water stands. The broken line in the diagram shows the approximate 

 condition of affairs during the summer of 1904. It comes ahnost to the surface in the 

 center and is nearer the surface at the west end and north side than at the shallow east 

 end. It seems to be held at the surface by the sphagnum which is very little disintegrated 

 in the center, while the soil in other parts of the swamp is physically in a very different 

 condition. This varying physical condition would greatly affect its moisture holding 

 capacity. 



We have here a dying tamarack swamp bounded by a marginal zone which seems to 

 have been influenced by other factors than the rest of the swamp. The distribution of 

 the swamp plants seems to have a definite relation to temperature, the physical character 

 of the soil, depth of the bog, and level of the ground water. The investigation of these 

 subjects is being continued and a fuller report will appear Tater. 



University of Michigan. 



Profile of bog from west to east. 

 Scale: Horizontal 80.4 cm=lmm, 



1. Sedges. 



2. Shrubs. 

 3 . Maples. 



4. Larix laricina. 

 C— C. Center. 

 M — M. Margin. 



vertical 61 cm=lmm. 



