241 
Eleocharis acicularis R. Br. Common in shallow water on 
alluvial and, sandy bottoms. 
Scirpus pungens Vahl. Common along sandy margins. 
Scirpus lacustris L. Lake and swamp margins ; common 
on both sandy and alluvial bottom. 
Scirpus smithii Gray. Occasional along sandy shores. 
Scirpus fluviatilis Gray. Very abundant in bottom-land 
swamps on alluvial bottom. Forming great tracts, to the ex- 
clusion of other plants, and contributing largely to the decay- 
ing vegetation of the backwaters. 
Scirpus atrovirens Mahl. Common, in marshy borders. 
Rhynchospora alba Vahl. Rare, along sandy margins of 
backwaters in shallow water. 
Zizania aquatica L. Forming meadows of considerable ex- 
tent in margins of lakes and more open swamps in the backwaters. 
Kquisetum limosum L. Sparingly present along springy 
margins of sandy shores. 
Azolla caroliniana Willd. This brilliant little eryptogam 
is locally abundant in warm sheltered regions of the back- 
waters in early summer. It is found principally in the dense 
mats of drifted Spirodela, where it forms bright red rosettes, 
the clusters sometimes forming an area several square feet in 
extent. 
The filamentous alge, principally Spirogyra and Zygnema, 
becomes very abundant in shallow waters in spring and early 
summer as the bottom-lands emerge from the receding flood. 
As the shores of the more permanent bodies of water are left 
bare, there remains upon them, half supported by the semi- 
aquatic vegetation, a thick felted mat of fading green, the 
strength and consistency of which are sufficient to justify the 
local name of “blanket moss.” Its rapid decay in warm shal- 
low water contributes immediately to the support of the plank- 
ton. 
VEGETATION AT THE SEVERAL STATIONS. 
Iilinois River (Station E.).—The following statements con- 
cerning the vegetation of the river are based upon many obser- 
