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Wolffia braziliensis Weddell. With the preceding but less 
abundant.* 
Sagittaria variabilis Kngelm. Abundant in shallow water 
along margins of lakes and swamps and in protected nooks 
along the river. On both alluvial and sandy bottoms, and often 
forming well-defined belts of vegetation. 
Triglochin palustris L. Occasionally found in marshes on 
alluvium. 
Potamogeton natans L. Widely distributed along margins 
of lakes, sloughs, and the river, in both quiet and flowing 
water, often occupying the open spacesin the littoral vegetation 
and among Ceratophyllum and Elodea. 
Potamogeton pusillus L, Rare, in open water of larger lakes. 
Potamogeton pectinatus L. Rare, in lakes and*in river near 
channels where there is considerable current. 
Naias flewilis var. robusta Morong. Frequent along shores 
of lakes and river in shallow water on alluvium. 
Dulichium spathacewm Pers. Occasionally found along allu- 
vial shores of quiet backwaters. 
Eleocharis palustris R. Br. Very common, forming patches 
of considerable extent along low sandy shores and in the mar- 
gins of Swamps. 
Eleocharis intermedia Schultes. Occasional in the mar- 
gins of lakes and swamps. 
Eleocharis tenuis Schultes. In shallow water in margins 
of swamps. Not common. 
*According to some criteria all of our representatives of the Lemnacee might be 
considered as part of the plankton. This is especially true of Wodfia, which is found 
in open water at all levels. Wind and current have much to do with its distribution, 
but, it has, nevertheless, a limnetic habit, comparable with that of many organisms of 
the plankton. Its general distribution and its small size afford further reason for 
regarding it as a part of the plankton of our locality. It was therefore not removed 
before measurement of the plankton. There are but few instances in our collections 
where it becomes a disturbing factor by reason of its predominance. The other 
members of the family are much larger and are more irregular in their distribution, 
and thus tend to distort the quantitative relations of the more typical plankton. For 
these practical reasons it seemed best to remove all specimens of these species from 
our catches before measurement, 
