50 MISSOURI BOTANICAL GARDEN. 
lakes of this series lie between Lakes Calumet and Michi- 
gan, representing various stages in the history of the 
pond from the open water to the typical prairie or forest. 
Lake Calumet is three and one-half by one and one-half 
miles in extent and its drainage is somewhat peculiar. In 
the southeast corner begins a stream, the first 200 yards 
of which forms the main stem of a Y. One of the arms 
of the Y stretches southward forming the Calumet River 
which, with its tributaries, drains a large section of the 
surrounding country. The other arm turns north and, 
after a somewhat tortuous course of six miles, flows into 
Lake Michigan. At some periods of the year, the current 
is flowing into Lake Calumet, at other periods it is flowing 
out. Conditions of rain fall, evaporationand other factors 
regulate this flow. Lake Calumet is, therefore, simply a 
bayou of the Calumet River and is subject to an average 
variation of twenty-two inches in level during the year. 
The southern end of the lake is thus afforded a consider- 
able amount of drainage and consequent change of water. 
On the same account the northern end of the lake is sub- 
ject to a much smaller degree of drainage, and even this 
small amount is much retarded by the great abundance of 
vegetation in this part. It is interesting to note in this 
connection that in the northern end are found such forms 
as Riccia and Ricciocarpus which are known to thrive well 
where the drainage is poor. A comparative study of the 
forms in the northern and southern portions of the lake 
could well be made with a view to discovering what influence 
the question of drainage exerted upon their determination. 
The western shores as well as the northern are exceed- 
ingly marshy. 
Dense formations of Scirpus lacustris extend for nearly 
one-half a mile into the lake, scattered patches being found 
far out from the general mass of vegetation. 
Occasional clumps of bulrushes are forming potential 
islands along the eastern shore and in the northeastern 
