48 THE ROYAL SOCIETY OF CANADA 



It is almost impossible in this part of the country to find a lake 

 of any size that has not been dammed, but Deer lake, the best example 

 studied, furnished evidence of similar progressive destruction. Coulter 

 (1904, pp. 46-48 and plate 6) and Transeau (1905, p. 371) describe 

 destruction of bog-forest that might be attributed to the same agency. 



The peculiar effect of increased fluctuation of water level upon 

 the floor of bog-forest has not, to our knowledge, hitherto been 

 described. Land surface and summer water-table approximate as a 

 result not of raising of the latter but of lowering of the former. 



The normal succession from hydrosere to xerosere is thus reversed. 

 At first, no doubt, there has to be destruction of the close canopy of 

 forest before the most photophilous forms can enter, but, thereafter, 

 as the forest floor subsides, the more hydrophilous types of under- 

 growth gradually supplant the less. Thus, Typha encroaches on 

 formations that normally encroach on it. It is difficult to describe 

 this as other than a retrogression. As the vegetation covering 

 becomes denser, affording greater protection, the process may tend 

 to slow down, and no doubt a turning point is reached. 



References 



Burns, A. P.: A botanical survey of the Huron River Valley. VIII. 



Edaphic conditions in peat bogs of Southern Michigan. Bot. 



Gaz. 52: 105-125, 1911. 

 Transeau, E. N.: The bogs and bog flora of the Huron River Valley. 



Bot. Gaz. 40: 351, 1905-6. 

 Coulter, S. M.: An ecological comparison of some typical swamp 



areas. Rep. Missouri Bot. Gard. Mar. 24, 1904. 



