30 UNIVERSITY OF MISSOURI STUDIES [172 



J. marginatus J. tenuis anthelatus 



J. aristulatus J. dichotomus 



J. tenuis J. acuminatus 



But the commoner types are either the grassy swale 

 with Glyceria nervata in the nucleus and Agrostis alba or A. 

 vulgaris as the chief associate; or the sedgy swale with Ca/rex 

 vulpinoides and C. conjuncta as chief species, and with other 

 marsh sedges and galingales (Cyperus spp.) as associates. The 

 black elderberry, Samhucus Canadensis, is common in the 

 swales north. 



2. Palustres uliginosae. Plants of the uliginose subzone. 

 Six open marsh societies are discernible : a. The marsh 

 meadow society, with various grasses as dominant plants, b. 

 The sedge-bog society with the coarse sedges dominant, c. The 

 rush-marsh society, the true rushes {junci) being dominant, d. 

 The smartweed community, e. The tickseed society with the 

 various species of Coreopsis and Bidens in control, f. The rag- 

 weed community. The first three associations constitute the uli- 

 ginose flora proper, the other three are lowland groups of allu- 

 vial and low prairie origin. Often it is impossible to tell to 

 which of the six types a marshy flat belongs, grasses, sedges, 

 rushes, smartweeds and tickseeds forming a complex group. 

 This is especially true of recently drained land, no one type hav- 

 ing yet become established. 



a. Uliginosae agrostidoides. The red-top association 

 is found in all grassy marsh meadows. Those about the water- 

 works reservoir are the best examples. The chief grasses are: 

 Panicum clandestinum Muhlenbergia Mexicana 



Leersia Virginica M. racemosa 



L. oryzoides (in wet Agrostis alba 



nuclei) 



