328 



LIST or' THE SPECIES OF THE SCIRPUS VALIDUS ASSOCIATION 



Dominant Species 



Scirpiis validus 



Secondary Species 

 Utricular ia vulgaris am eric ana 

 Acoriis calamus (a very little on 



the lower border) 



Relic vSpecies 

 Nymphaea advena (scarce) 



Spartina michaiixiana (dwarfed 



and but little of it) 

 Rwiiex britannica 



Typha latifolia (only on the lower 

 border and scarce) 



Invading Species 

 Scirpus aiiicricanus (on the upper border) 



THE SCIRPUS AMERICANUS ASSOCIATION 



As has been mentioned, the Scirpus americaiius association occu- 

 pies shallower water than the Scirpus validus association. The ac- 

 cumulation of humus is greater, and it is sometimes peaty in nature. 

 This association does not occupy ground that is permanently out of 

 water, although sometimes during dry seasons it may be a decimeter 

 or two above the water-level. In such cases, however, the ground is 

 still, as a rule, thoroughly soaked by means of capillary attraction or 

 other agency. If this is not so, the Scirpus stems wdll become dry 

 and brown, but upon restoration of the water to its former level they 

 usually become green again. These light green stems give the char- 

 acteristic color-tone to the association. When growing in nearly pure 

 damp sand, the Scirpus stems are often spirally twisted — a modifi- 

 cation exhibited also by Juncus halticiis littoralis, as mentioned on 

 page 277. 



LIST OF THE SPECIES OF THE SCIRPUS AMERICANUS ASSOCIATION 



Dominant Species 

 Scirpus americamis 



Secondary Species 

 Triglochin maritiiua 

 Salix Candida 

 Bidens trichospcriua tcuiiiloba 



Relic Species 

 Alisnia plantago-aquatica 



Bleocharis acuminata 

 Briophornm angtistifolium 

 Rynchospora capillacca Icznscta 



Scirpus validus (scarce) 



