10 UNIVERSITY OF MISSOURI STUDIES [158 



The Plains Flora falls into five main societies : The 

 Aquatic (Aquatiles); The Palustrous (Palustres); The Ri- 

 parian (Ripariae); The Prairie Meadow, the plains flora 

 proper, (Campanales); and the Alkali Flat (Alkalinae). 



a. Aquatiles. The Aquatic Flora is found in lakes and 

 streams. It consists of submerged or floating aquatics pond- 

 weeds, duckweeds, water-milfoils, hornworts, water starworts, 

 besides various algae. It is seen best in Owen's lake and 

 Boulder lake, which while about twenty feet deep, are very 

 brackish. The slower streams also have aquatic plants, as do 

 likewise the aqueous nuclei of swamps and swales. The fol- 

 lowing is a list of typical species : 



Potamogeton lonchites L. minor 



P. heterophyllus Ceratophyllum demersum 



P. foliosus Callitriche palustris 



P. pectinatus C. bifida 



P. Spirillus Myriophyllum spicatum 



Zanichellia palustris Limosella aquatica 



Lemna gibba 



All the above species occur in the eastern United States. 



b. Palustres. The Palustrous, or Swamp Flora is found 

 in bogs, in swales, along ditches, and about the miry margins 

 of ponds and lakes and streams. It consists of rushes, bul- 

 rushes, sedges, swamp grasses, sweet flags, cat-tails, stick- 

 tights, swamp asters, water peppers, and various other plants. 

 I have included here the whole subaquatic flora, since the for- 

 mation is so slight that it is best treated as a whole without 

 separation into amphibious, limose, paludose, and uliginose 

 societies. The following are characteristic species : 



Equisetum arvense Typha lati folia 



E. laevigatum Alisma Plantago 



