Jan., 1922] UPHOF — PLANTS IN SOUTHEASTERN MISSOURI 
II 
liniana Willd. is also very common in quiet or almost stagnant waters, 
so covering the surface of the water as to give the appearance of a large 
lawn. Riccia natans L. is frequently to be found but is never as common as 
the other species belonging to the floating flora. These species are, apart 
from several algae, the first appearance of any vegetation in these watery 
areas. 
About seven meters below the water surface there are a few species of 
plants rooting in the mud ; a very few individuals may here be found of 
Isoetes Engelmanni A. Br.; between the depths of five and seven meters 
a number of submerged species are prevalent. Where the water is clear, 
large areas can be noticed of "meadows" with Elodea canadensis Michx. ; 
where this growth is not as dense, Potamogeton Hillii Morong, P. pusillus L., 
and Najas flexilis (Willd.) Rostk. & Schmidt are present; and occasionally 
Ceratophyllum demersum L. and some Vallisneria spiralis L. In a few ponds 
I found whole areas filled with Myriophyllum heterophyllum Michx., and 
nothing else. In slowly flowing streams and little rivers, Batrachium aqua- 
tilis L., and especially Heteranthera graminea Vahl, are very common; 
the Black River is for several miles covered with the latter species. 
Fig. I. A swamp formation. A, Hibiscus, Sium, Cicuta, Rumex, Iris, Sagittaria, 
Mimulus, Lobelia. B, the same, and Phragmites, Typha, Acorus, Sparganiiim. C, 
Scirpus, Nelumbium. D, Nymphaea, Nuphar. E, Potamogeton Hillii, Najas, Elodea, 
Ceratophyllum, Isoetes. F, Isoetes. 
The facies of the water lilies and their associates are formed at a depth 
of from two to four meters below the surface; these aquatilis natantes form 
dense masses of Nymphaea odorata Ait. and Nuphar advena Ait. Commonly 
found in these places are Potamogeton hybridus Michx., P. americanus C. & 
S., and P. natans L.; where the growth of water lilies is too dense the Pot- 
amogetons are unable to grow. Frequently they form pure associations 
without any other water plant. Between these are often found the above- 
described submerged species; whereas Isoetes Engelmanni becomes more 
frequent, /. melanopoda J. Gay is also noticed. 
Toward the border of the lake the water-lily association includes con- 
siderable tracts of Nelumho lutea (Willd.) Pers. often reaching the border 
of the lake and large pools. They may be considered as forming an in- 
