344 MIXXESOTA nOTAXlCAL STUDIES 



list are relicts of the preceding associes. With these species may 

 also be found : 



Carc.v (jynocratcs Carex trisperma 



Carcx leptalea Coptis trifolia 



Carer paiiperciila pallens Ilabcnaria dilatafa 



Carc.v scirpoides Ilabcnaria hypcrborea 



Carcx tcncUa Habcuaria obfiisala 



Where Sphagnum has died out leaving mounds of hunnis, and 

 along the border of the swamp where filling up has resulted in death 

 of the Spliagiiitju, the following plants are characteristic: 



Carcx tcncUa Linnaea borcaJis 



Carcx trisperma Maiantheiiniui canadense 



Chiogcucs hispidula Osnntuda ciiniajnoineiim 



Clintonia borealis Osmitnda claytoniana 



Coptis trifolia Pctasifcs paliiiafa 



Coruus canadensis Pyrola asarifolia 



Cypripcdium hirsuium Pyrola sccnnda 

 Cypripcdiiini parviflonim Tricntalis amcricana 

 Dryopfcris cristafa 



Chiogenes and Linnaea are found often on decayed fallen logs, 

 where they usually form a dense mat over the surface. Many of 

 the ])lants of the above list are to be found typically on swamp 

 borders. Gaultheria procnmbens has been found occasionally with 

 the above plants. 



(7) Abics-Bctula Associes 



The filling-up of a swamp by the washing in of soil from the 

 sides and in part also by the accumulation and subsequent decay of 

 Sphagnum and other plant remains results in the formation of a soil 

 rich in humus, but one in which the water-content is much reduced 

 as compared with that of the substratum of the Larix-Picea or 

 Chamaedaphne- Andromeda associes. The formation of humus and 

 reduction of w^ater-content favors the invasion and establishment of 

 the plants of the Abies-Befula associes. Drainage of a swamp would 

 accelerate the appearance of subsequent stages. 



Consocies : The following are the usual dominants: Abies 

 halsamca, Bctula papxrifcra, B. Intea, Picea canadensis and Thuja 

 occidcntalis. 



