42 2 George E. Nichols, 



C. THE ASSOCIATION-COMPLEXES OF UNDRAINED SWAMPS 



Ecological characteristics of the more important hog species of 

 Sphagnum. — Emphasis has been laid earher on the prominence 

 in bogs of the sphag-num mosses. Allusion has also been made 

 to differences in the ecological relations of various species, in 

 their manner of growth, and in the role which they play in bog 

 development. It seems appropriate at this point to sum up 

 briefly, with reference primarily to their ecological relations, the 

 essential features of the more important species of Sphagnum 

 which grow in the bogs of this region. These may be divided 

 more or less definitely into five groups, as follows. 



Group I. Plants primarily aquatic, floating at or near the 

 surface of the water. vS". cnspidatum: commonly yellowish 

 green in color, limp and flaccid, with a delicate, feathery appear- 

 ance ; when growing emersed, stems usually prostrate and 

 trailing or creeping. The var. Torreyi is very robust, more 

 rigid than the typical form, and ordinarily a dirty brownish 

 green in color. S. Pylaisci: dark purple to nearly black in 

 color; soft and delicate, but as a rule scarcely flaccid; slender, 

 with sparsely developed, short branches ; when growing emersed, 

 stems prostrate and trailing or semi-erect ; perhaps the most 

 easily recognized of any native sphagnum. 



Group 2. Plants semi-aquatic, amphibious ; occasionally com- 

 pletely submerged and with a habit similar to that of S. cnspida- 

 tum, but more commonly with the tips of the shoots projecting 

 well above the surface of the water; quite robust, fairly rigid, 

 erect. vS. Dusenii: in color, usually green, more or less tinged 

 with yellow-brown. 5^. pulchrum: in color, olive-green to 

 brownish green ; commonly grows emersed, forming dense but 

 rather loose, soft cushions (see further under group 4). 



Group 3. Plants primarily non-aquatic, commonly growing in 

 low, wet, boggy grounds. S. tenellum: erect, slender, fragile, 

 usually occurring in dense, loose masses and forming beautiful, 

 soft, low mats; in color, ordinarily yellowish green; one of the 

 most delicately lovely of all the sphagnums. 



Group 4. Plants mainly non-aquatic, though commonly grow- 

 ing in very wet places and occasionally submersed ; usually very 

 robust, erect and rather rigid ; when emersed, forming dense, 

 rather compact masses and building up fairly firm cushions ; 

 submersed forms quite flaccid. 5". papillosum: in color, generally 



