46 THE ROYAL SOCIETY OF CANADA 



Over the greater part of the area, however, the dominant new 

 growth consists of an upper stratum (20 ft. high, or less) of thrifty 

 black ash {Fraxinus nigcr) and swamp maple {Acer ruhrum), with an 

 undergrowth of shrubs (Alnus incana, Ilex verticillata, Salix and 

 Cornus spp.) and a bottom stratum that varies with the level of the 

 depression from limnophytic forms, such as Typha, Alisma, Sagittaria, 

 Carex, Eleocharis, etc., to mesophytic types — -asters, Chelone, Heuchera, 

 grasses and mosses. 



Water levels. — ^The water table in August, 1921, was found to be 

 13^ to 23^ ft. below the present level of the old forest fîoor. Obser- 

 vations elsewhere and records by Burns (1911, 115-121) show that this 

 is more than sufificient elevation for a tamarack or cedar bog-forest. 

 The lake level at the same time was about 680 feet above sea level 

 (falling later to a still lower level). The remains of old forest floor 

 ranges from 682.5' to over 684', and while the large trees at these 

 levels are either dead or dying, there are healthy cedar saplings at 

 682.5', spruce at 682.8', and pine at 683'. The advantage possessed 

 by these young trees is simply that their smaller spread of roots 

 enables them to find sufficient substratum on the hummocks of old 

 forest floor that still persist. Conversely, the cause of injury to the 

 older trees is apparently the erosion or decay of their original root- 

 run, and not an excessively high water level during the growing 

 season. 



The present normal level of spring floods, however (probably 

 about 683'), is sufficient to submerge the greater part of the old forest 

 floor, and there is evidence of still higher floods about 30 years ago. 

 Coastal erosion can be proved to have been much greater than then 

 now. While flooding during the dormant period does not directly 

 injure trees in swamps, it has probably done so indirectly through 

 destruction of the peaty floor. This may have been brought about 

 partly by actual suspension and washing out of material and partly 

 by effecting increased decomposition and shrinkage of the organic 

 matter. Regular inundation with lime containing water must 

 diminish soil acidity, and since the high spring level is accompanied 

 by a low summer level, oxidation (eremacausis) is favoured (see 

 Transeau, 1905-6, p. 371). It is significant that the new vegetation 

 is hydrophtic rather than oxylophytic. The present character of the 

 peaty floor also suggests advanced decomposition. 



Rate of tree groidh.- — A study of the trees that still survive enable 

 us to trace the progress of untoward conditions in these bog-forests. 

 The general age of renewal shoots (orthotropous lateral shoots pro- 

 duced after death of original branches) is about 30 years as a rule, 



