20 UNIVERSITY OF MISSOURI STUDIES [[6i 



Scirpus Americanus Heleocharis palustris 



S. lacustris H. ovata 



S. fluviatilis (rare) Juncus effusus (local) 



d. Amphibiae glycerioides. The reed association of 

 amphibious grasses and grass-like sedges is but feebly developed, 

 the two most typical reed grasses, Zisania aquatica and Phrag- 

 mites communis, not being known in the region. Besides cer- 

 tain carices, which are better regarded as belonging to the pal- 

 udose subzone, the following are the chief species : 



Leersia oryzoides Dulichium spathaceum 



Spartina cynosuroides (local) 



(rare) Eriophorum lineatum 



Glyceria nervata Scirpus atrovirens 



G. fluitans (rare) 



e. Amphibiae cicutoides. The cowbane association 

 of tall, rather bushy plants, which are seldom gregarious, con- 

 sists mainly of UmbelUferae and Polygonuceae. A partial list 

 follows : 



Rumex crispus Cicuta maculata 



R. verticillatus Slum cicutaefolium 



f. Amphibiae jussieuoides. The primrose-willow as- 

 sociation consists of recumbent, partly floating amphibious 

 plants, which, when terrestrial, are creeping or decumbent. 

 There are but three plants that behave thus. Polyg07iunt emer- 

 sum is confined to the wettest parts of swamps. Jjissieuadi^usa 

 is local in ponds, and Bacopa rotundifolia occurs with Nelum- 

 bo lutea in a pond near Rocheport. 



2. Marginales limosae. Plants of the limose subzone. 

 The limose subzone comprises muddy shores and low alluvial 

 flats which are subject to more or less frequent inundation. 

 The plants are partly of amphibious and partly of littoral types, 

 while at the outer rim of their subzone they often coalesce with 



