404 Proceedings Portland Society Natural History 



stalks and branches of these shrubs furnish a frame work 

 on which various sphagnums find a foothold and develop in 

 great profusion. The important role which these mosses 

 play in bog formation has been emphasized by most writers 

 and summed up in detail by Cooper (4) and Nichols (23). 



The continual growth of the mat lakewards and the ac- 

 companying filling up of the pond from within finally re- 

 sults in the complete elimination of any open water. At 

 first the continuous mat, thus formed, may still overlie wa- 

 ter, in which case it constitutes a quaking bog, but as more 

 and more debris falls down from the under side of the mat 

 the bottom is built up and sooner or later the mat becomes 

 grounded. When this has occurred the bog is drier 'than 

 at any previous time during its formation. 



During the course of its development the sphagnum mat 

 becomes colonized with various other plants. In cases 

 where sedges are the pioneer plants these may at first 

 dominate an area of considerable extent on the mat itself, 

 but later they are invaded by shrubs. Where shrubs are 

 the pioneers the mat from the very first supports a vegeta- 

 tion consisting of both sedges and low shrubs growing to- 

 gether. In either case as the mat becomes drier, larger 

 shrubs begin to come in and eventually trees, such as the 

 larch and black spruce (Picca mariana ). Each individual 

 bog varies somewhat as to its component species, but the 

 following list comprises the plants ordinarily present : 



Herbaceous Species 



Lycopodium inundation Smilacina trifolia 



Eriophorum callitrix Calopogon pulchellus 



Eriophorum virginicum Pogonia ophioglossoides 



Rynchospora alba Drosera rotundifolia 



Carex exilis Drosera longifolia 



Carex trisperma Sarracenia purpurea 



Carex paupercula var. Utricularia cornuta 



irrigua Solid a go uniligulata 



