58 Trans. Acad. Sci. of St. Louis. 



Lemna perpusilla, and var. trinervis, Wolffia Columbiana. 

 Jussiaea repens is also often found floating free. 



CLASS II. WATER PLANTS ROOTED IN THE SOIL. 



This class is represented here and there over the entire 

 State, in ponds, springs, the central part of marshes where 

 there is visible water, and (especially westward) in slow-flow- 

 ing streams. Some are submersed, when the leaves are 

 finely divided, others have floating leaves, but the vegetative 

 portion does not rise above the surface of the water, except 

 as the water may evaporate and leave the plant in the mud. 

 The flowers are pushed above the surface but the fruit is 

 usually submersed. 



Ranunculus divaricalus, R. multifidus, Kelumbo lutea. The 

 leafy blades of the last are usually raised out of the water, yet 

 the plant should undoubtedly be classed here. Nympliaea 

 odorata, JSTuphar advena (leaf blades frequently emersed), 

 Nasturtium officinale, Myriophyllum spicatum, M. scabratum, 

 Callitriche heterophylla, Jussiaea ?*epens, Ilerpestis rotundi- 

 folia (also a swamp plant), Elodea Canadensis, Heteranthera 

 limosa, H. reniformis, H. graminea (these three grow also in 

 the mud), Polamogelon (several species), Ruppia maritima y 

 Zannichellia palustris. 



CLASS III. SWAMP PLANTS. 



The plants are rooted in the soil, which is saturated with 

 water and may be submersed, but the vegetative organs extend 

 above the water when it is present as a sheet. This class is 

 usually found around the borders of the preceding class and 

 also along rivers and ponds in which the preceding class may 

 be absent. The species are too numerous to give a detailed 

 list. But we may distinguish a few communities which often 

 have many species in common but which possess a distinctive 

 physiognomy. 



Reed-Sioamps. These occur in swampy depressions or 

 along water-courses. The plants are mostly with upright 

 leaves and are chiefly monocotyledons. During the rainy 

 season (spring and early summer) the swamp may show much 

 open water between the plants, but later the water may 



