356 MINNESOTA BOTANICAL STUDIES. 
ATTACHED AQUATIC PLANTS WITH NATANT LEAVES. 
Castalia tuberosa, Potamogeton lonchites, 
LVelumbo lutea, 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, Velwméo lutea, and the yellow pond-lily, 
Nymphea 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.) Incase 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, 
Elleocharts 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 
