356 MINNESOTA BOTANICAL STUDIES. 



ATTACHED AQUATIC PLANTS WITH NAT ANT LEAVES. 

 Castalia tuberosa, Potamogeton lonchttes, 



Nelumbo hitea, Potamogeton natans, 



Nymphaea advena, Sagittaria cuneata. 



Nearly every one who has ever visited any of the lakes or 

 rivers of Minnesota is acquainted with at least one representa- 

 tive of this group, the white water-lily, Castalia tuberosa. This 

 with the Indian lotus, Nelumbo lutea, and the yellow pond-lily, 

 Nymphcea advena, all of which are members of the water-lily 

 family, are the most conspicuous and beautiful of our river 

 plants. They cover large areas of shallow water for sometimes 

 a mile or more in extent. It may be of interest to call attention 

 to the methods of adaptation of these plants to their aquatic 

 habitat. The white water-lily and the yellow pond-lily carry 

 their natant leaves on long flexible petioles which allow the 

 leaves to remain upon the surface for variations of several feet 

 in the height of the water. The Indian lotus, however, carries 

 the leaf-blades upon stiff strong petioles some of which are car- 

 ried up to the water surface and others are raised from one to 

 three feet above the water. (Plate XXV., A.) In case the water 

 rises the natant leaves are destroyed but those that are raised 

 above the surface remain useful to the plant and may in this way 

 be caused to float. The projecting leaves are not conspicuously 

 modified in any way from those that were originally natant. 



Both the Indian lotus and the white water-lily are abundant 

 in the sloughs of the Mississippi river at Jefferson. The yellow 

 pond-lily is not so abundant as either of the other two. The 

 Potamogetons with floating leaves may be found growing with 

 the water-lilies or in small patches scattered throughout the 

 sloughs. They never cover very large areas to the exclusion 

 of other plants. 



ADAPTIVE SHORE PLANTS. 



Alisma -plantago-aquatica, Sagittaria latifolia, 



Eleocharis acicularis, Sagittaria rigida, 



Nelumbo lutea, Scirpus lacustris. 

 Polygonum emersum, 



The plants living on the shores of the lakes and sloughs must 

 adapt themselves to life under the varying conditions in which 

 they may be placed by the rise and fall of the water. During 



