52 MISSOURI BOTANICAL GARDEN. 
may be mentioned the Potamogetons, Heteranthera gram- 
inea,- Pontederia cordata, Brasenia peltata, Elodea Cana- 
densis, Myriophyllum and Ceratophyllum. Cowles* has 
listed the character plants of this area and discussed its 
dynamics to some extent. An exhaustive study of the 
history of this and other areas in the pond-swamp-prairie 
series would form a valuable addition to ecological liter- 
ature. 
5. HORSE-SHOE* LAKE, AN OLD “ OX-BOW’’ OF THE MISSISSIPPI. 
In the lowlands of the Mississippi opposite Saint Louis 
there are many of these depressions which have once been 
a part of the river bed, but are now cut off by the shifting 
of the channel. One may find them in every stage of ad- 
vancement, from the open lake through the marsh to the 
solid ‘* bottom land.’’ As has been said of the pond- 
swamp-prairie series, so it may be stated of this region, 
that a thorough investigation of the conditions at work in 
filling up these lakes and swamps, and the succession of 
forms concerned in the process would comprise a welcome 
contribution to this department of science. 
On the northern shore Nelumbo lutea is the prevail- 
ing type plant farthest from the shore. An occasional 
Nymphaea odorata may be observed. (Plate 8.) 
Scirpus maritimus 1s the prominent water margin plant, 
extending up the marshy shore 40 or 50 feet. This gives 
the tone to the landscape at this point, but an important, 
though inconspicuous, plant which borders it lakeward is 
Jussiaea repens. Associated with the Scirpus maritimus 
and partially concealed by it is a species of Eleocharis 
which becomes very vigorous and abundant in places where 
the taller bulrush is more sparse. 
In other places the Eleocharis has been forced more to 
* Cowles, H.C. The Plant Societies of Chicago and vicinity. (Bul- 
letin of the Geographic Society of Chicago. 2341. 1901.) 
