340 .MINNESOTA I50TAN1CAL S'rUl)ll':S 



Ac or US calamus Polygonum amphibium 



Alisma plantago Sagittaria arifolia 



EleocJiaris palnstns Sparganium eiirycarpum 

 Nauuihcrgia thyrsi flora 



The last two named are never abundant, but are usually repre- 

 sented by a few individuals. Naumhcrgia becomes more abundant 

 in the following associes. 



(4) Carcx Associes 



The reaction of the plants of the Scirpns-Zizania associes in 

 building up the lake shores, by retaining the sedimentary material 

 washed into the lake and by the accumulation of decayed plant re- 

 mains, results in a low^ering of the water-level. This permits the 

 invasion and establishment of species of Carex, which are the domi- 

 nants of this associes. The lowering of the water-level of the lake 

 by drainage or by any other cause would bring about a change of 

 conditions favorable for the establishment of species of this associes. 



Consocies : Several species of Carex are the dominants of this 

 state. The following are the typical species : 



Carcx aquafilis Carcx trichocarpa 



Carcx filiform is 



Carex aqitatilis and C. filiformis are less abundant than C. tricho- 

 carpa, although in some places C. filiformis occurs exclusively. Usu- 

 ally the Carex zone is narrow, varying from three or four feet to 

 thirty or forty, although in exceptional cases it may be much wider. 

 In many instances the Scirpus-Zizania associes is poorly developed, 

 being represented by a sparse growth of Zizauia or of Zisania and 

 Scirpus, or it may be entirely absent, the Carex associes directly 

 following the Castalia-Nymphaea associes. The sedges push out 

 farther into the water from year to year by the development of root- 

 stocks and cause a rapid filling of the lake, thus enabling the follow- 

 ing associes to become established. 



Secondary species : The following species of sedges and grasses 

 are usually present, but with the exception of Carcx diandra never 

 appear in sufficient number to be regarded as consocies. This may 

 be true of Carcx diandra in some cases. 



Carex bebbii Carcx sarfzvelli 



Carex diandra Phalaris ariindinacea 



