Vegetation of Northern Cape Breton. 361 



developed. Where, however, as along the south shores of several 

 of these bogs, shade conditions preclude the growth of the 

 sphagnums, no mat is developed (see further on p. 363). So 

 luxuriant, as a rule, is the development of the sphagnums that 

 the important role played by the cassandra is liable to be over- 

 looked ; but if a newly formed "sphagnum mat" be dug into, the 

 woody ribs formed by this shrub will usually be found. 



In some instances, certain sedges play a role similar to that 

 just ascribed to the cassandra. Certain of these, e. g., Carex 

 filiformis, in contrast to the shrubs, are quite capable of forming 

 a mat themselves, independently of any assistance from the 

 sphagnums. But, as a rule, the sphagnums make their appear- 

 ance at an early stage in the history of the mat and thereafter 

 play an important part in its development : ordinarily they 

 spread so rapidly and grow with such luxuriance as to quickly 

 become the predominant element of the plant cover. Various 

 features associated with the formation and growth of floating 

 mats are discussed further in the following paragraphs and in 

 later pages, in connection with the swamps of the highland. 



On the "sphagnum mat" thus formed, in greater or less 

 abundance, grow various sedges and shrubs which, by their roots, 

 rhizomes and trailing stems, tend to bind together and consoli- 

 date the otherwise loose structure. Characteristic species are 

 the following: 



Eriophorum callitrix Kalmia polifolia 



Eriophorum virginicum Ledum groenlandicum 



Rynchospora alba Vaccinium macrocarpon 



Carex canescens disjuncta Vaccinium Oxycoccus 



Carex paupercula irrigua Menyanthes trifoliolata 

 Carex stellulata 



Along the wet margin of the mat, where it borders on the 

 marginal ditch (see further below), and in the ditch itself where 

 this is swampy, commonly grow various forms which one 

 ordinarily associates with well-drained swamps ; among them : 

 Sparganium americanum, Iris versicolor, Alnus incana, Myrica 

 Gale, Rosa nitida, Ilex verticillata, Hypericum virginicum, 

 Lysimachia terrestris, and Lycopus americanus. These plants 

 seldom occur in the older parts of the bog. 



Trans. Conn. Acad., Vol. XXII 22 1918 



