444 BOTANICAL GAZETTE [DECEMBER 



mara, Impatiens biflora, Eupatorium perfoliatum, Calamagrostis 

 canadensis, Dryopteris thelypteris, D. spinulosa intermedia, Doel- 

 lingeria umbellata, Lactuca spicata, Coptis trifolia, Boehmeria cylin- 

 drica, Onoclea sensibilis, Marchantia polymorpha, and Rosa Carolina. 

 The further development of these societies under present condi- 

 tions will bring about a complete change. There can be no doubt 

 that the poplars and red maples are the coming trees, with elm a 

 close third. When these have become sufficiently large and numer- 

 ous to overshade the shrubs, the latter will be killed but, and we 

 shall have in their place the maple- elm forest common to the low 

 grounds. The shrubs, however, are capable of persisting for a great 

 length of time, because of the difficulty of tree seedlings obtaining a 

 start beneath them. 



THE CHELSEA BOG. 



Of the bogs which have been subjected to clearing, burning, and 

 ditching, by far the most interesting in this region is located just to 

 the southeast of the town of Chelsea. It covers an area of about 

 50 acres (20 hectares), and the peat is reported to be 40 feet (i2 m ) 

 thick at the deepest places. The divisions into societies, as indicated 

 on the map (fig. n), are based on the most general characters of the 

 vegetation. There are gradations between all of the societies, and 

 these are so gradual that it is difficult to determine definitely the 

 boundaries. Further, owing to the tendency of many of the shrub 

 species to form dense local growths by the development of stems 

 from underground shoots, the smaller associations are very diverse 

 in different parts of the same society. 



Birch-vaccinium society. This mixed society of bog shrubs occupies 

 about one-fourth the area of the bog. Its substratum consists of 

 peat standing about a foot above the average water level. The 

 dominant plants are Betula pumila, Vaccinium corymbosum, Rubus 

 frondosus, Aronia nigra, Vaccinium canadense, and Pteridium 

 aquilinum. Just as common perhaps, but of lower growth, are 

 Rubus hispidus, Spiraea salicifolia, S. tomentosa, Aralia hispida, 

 Chamaedaphne calyculata, and Rumex Acetosella. The ground 

 covering, except beneath the dense shade of the shrubs, is made up 

 of Polytrichum juniperinum. There are many small areas of which 

 this plant now holds exclusive control, and forms a rich carpet of 



