Wheeler : FLORA OF SOUTHEASTERN MINNESOTA. 357 



low stages they may be left out of the water entirely and when 

 the water is at its height most of them are nearly or quite sub- 

 merged. The plants adapting themselves to these conditions 

 might be considered as the Sagittaria group, for the two Sagit- 

 tarias latifolia and rigida are the most abundant shore plants 

 with the possible exception of Eleocharis acicularis. Nelumbo 

 lutca may often be seen in times of very low water, grow- 

 ing on the muddy banks entirely emersed holding its leaves 

 erect two or three feet above the mud, while the Castalia when 

 placed under these conditions lodges its leaves on the mud where 

 they soon die. Polygonum emersum covers many banks to the 

 exclusion of other vegetation. It is adapted to living on the 

 exposed mud or in the water but under the latter conditions it 

 always projects its leaf-bearing stems out of the water and keeps 

 the foliage leaves emersed. 



WET MEADOWS OF THE RIVER VALLEY. 



During a large part of the growing season the wet meadows 

 of the river bottoms are submerged. When they are exposed 

 for a sufficient length of time to become somewhat dry the 

 grasses are generally cut for hay. The plants living under 

 these conditions are mostly coarse grasses and sedges. No trees 

 but willows seem to be able to live upon these meadows and 

 they do not then attain tree size. Some of the plants forming 

 the vegetation of the wet meadows are : 



Asclepias incarnata, Scirpus atrovirens^ 



Cyperus esculentus, Scirpus cyperinus, 



Eleocharis acicularis, Stum cicutaefolium, 



Elymus virginicus, Sparganium eurycarpum, 



Eragrostis hypnoides, Spartina cynosuroides, 



Eupatoriiim purpureum , Vernonia fasciculata , 



Homalocenchrus virginicus, Zizania aquatica. 

 Penthorum sedoides, 



MUD-FLAT VEGETATION. 



The mud-flat comprises the highest land of the islands. It is 

 flooded only during the early summer but on account of its 

 growth of timber and shrubs the soil remains wet during the 

 entire year. The largest trees growing anywhere in this region 

 are found on the mud-flats of the Mississippi river. 



