364 George E. Nichols, 



Hypnum Schreberi. Here and there, even in an old bog, there 

 are moist or wet depressions in which may occur the more hydro- 

 phytic species of Sphagnum, together with Hverworts such as 

 Cephalozia fluitans and Mylia anomala and mosses such as 

 Calliergon stramineiim and Drepanocladus fluitans. 



Scattered about over the sphagnum substratum, and varying 

 greatly in abundance locally, are diverse trees, shrubs, and herba- 

 ceous plants. The characteristic and omnipresent tree of bogs 

 is the black spruce. Invariably dwarfed in size, it commonly 

 forms low, scraggly clumps, the result of layering followed by 

 the death of the parent tree or of the original trunk.^^ 



The predominant bog shrubs are ericads : Chamaedaphne 

 calyculata, Gaylussacia baccata, Kalmia angustifolia, K. polifolia, 

 and Ledum groenlandicum, to which should be added the semi- 

 shrubby forms, Chiogenes hispidula and Vaccinium Oxycoccus. 

 Three non-ericaceous shrubs also are usually well represented: 

 Amelanchier sp., Nemopanthus mucronafa, and Viburnum cas- 

 sinoides. The most important herbaceous species are Osmunda 

 cinnamomea, Eriophorum callitrix, E. virginicum, Rynchospora 

 alba, Carex trisperma Billingsii, and Cornus canadensis. Three 

 orchids, Habenaria blephariglottis, Pogonia ophioglossoides, and 

 Calopogon pulchellus, are conspicuous when in flower ; Drosera 

 rotundifolia is common, and Lycopodium inundatum occasional 

 in moist depressions; Smilacina trifolia occurs locally in wet 

 places ; Empetrum nigrum grows abundantly in the drier portions 

 of one bog ; while Arceuthobium pusillum is a frequent parasite 

 on the black spruce. 



d. THE ASSOCIATION-COMPLEXES OF POORLY DRAINED SWAMPS 



Under the head of poorly-drained swamps are classed swamps 

 of an intermediate character : swamps whose vegetation resembles 

 in some respects that of well-drained swamps, in other respects 

 that of undrained swamps. Boggy swamps of this character 

 are of far more general occurrence than are those of the more 

 extreme types, such as have been described in the foregoing 

 paragraphs. 



" Ganong ('97: see quotation on p. 447 of the present paper) has 

 called attention to layering as a means of reproduction in Picea mariana, 

 and the phenomenon has been discussed in some detail by Cooper ('11) 

 and Fuller ('13). 



