ECOLOGICAL RELATIONS OF THE FLORA. 43 



Detail of the Alnus Association. 

 Dominant Species: 



Myrica gale. 



Alnus incana. 

 Sub-Dominant Species: 



Osnnaida regalis. 



Larix laricina. 



Thuja occidentalis. 



Salix longi folia. 



Populus tremuloides. 



Spiraea salicifolia. 



Potentilla fructicosa. 



Rosa Carolina. 



Pyrus melanocarpa. 



Ilex verticillata. 



Rhus vernix. 



Cornus stolonifera. 



Asclepias incornata. 



Cephalanthiis occidentalis. 



Verbena hastata. 



Lactuca^canadensis. 



Wooded Swamp Formation — Birch-Willow Association: From the 

 Alnus association surrounding the meadow there was an easy gradation 

 to the wooded swamp, the birch-"uillow association, found at older or 

 innermost and lower parts of the Point. The damp conditions of the 

 thickets persisted, but, while the thicket growth in the formation was 

 frec[uently so den.se that it was hard to penetrate, at other places it 

 was thinned so that there was an approach to the open woods which 

 was the climax of this succession. In the wooded swamps we found 

 that the shrubs and bushes which characterized the younger thickets 

 diminished and there was a gradual increase in the dominance of the 

 elms, maples, and birches over the alders. Xo detailed lists were made 

 for this formation. 



An examination of the lists given above will show that the swamps 

 on Sand Point belong .to the "drained" as distinguished from the ''un- 

 cb-ained" type, of Cowles (1901) and Transeau (1903). A few bog 

 forms such as Menyanthes trifoliata, Andromeda polifolia, Cassandra, 

 tamarack and black spruce are occasionally present but only in small 

 numbers. The fact that the bog societies are dominant in no place 

 in the sand region is very probably due to the fact that the sand}' sub- 

 stratum affords better drainage conditions than is most favorable 

 for the bog forms. (Gunnar Andersson, 1896, p. 433. et seq.) But 



