40 MISSOURI BOTANICAL GARDEN, 
the work has been done partly in connection with the 
Hull Biological Laboratory, University of Chicago, and 
partly in connection with the Shaw School of Botany, 
Saint Louis. The author herein acknowledges with grati- 
tude the kindly assistance of his associates in both these 
laboratories, and, especially, the helpful suggestions of 
Professor John M. Coulter and Doctor Henry C. Cowles of 
the University of Chicago, and Professor William Trelease 
of the Shaw School of Botany. The maps and photo- 
graphs were made by the author especially for this paper. 
GENERAL VIEW OF THE AREAS STUDIED. 
The areas investigated mostly lie along a line about 800 
miles long running from near Mackinac ‘Island, Michigan, 
southwesterly to the vicinity of Paragould, Arkansas, as 
indicated in the accompanying map. (Frontispiece. ) 
These studies comprise the following : — 
1. A drained swamp along the Crooked River in the 
northern part of the lower Michigan peninsula. 
2. An undrained tamarack-black spruce swamp sur- 
rounding a small lake on North Manitou Island, Michigan. 
3. A slavidy drained arbor-vitae swamp lying along the 
outlet into Lake Michigan of a larger lake on the same 
island. 
4. The small, swampy lakes south of Chicago: Lake 
Calumet as a type. 
5. Horse-shoe Lake in southwestern Illinois, an old ox- 
bow cut off from the Mississippi River. 
6. A cypress-tupelo gum swamp along the Saint Francis 
River in northeastern Arkansas. 
1. RIVER SWAMP ALONG CROOKED RIVER. 
At the mouth of the Cheboygan River, near the northern 
extremity of the lower Michigan peninsula, a dam has been 
constructed which has considerably enlarged the areas of 
