272 BOTANICAL GAZETTE [ocToBER 
4. The vertical succession of societies which build up the drained 
swamp may culminate in tamarack and other plants with xerophytic 
adaptations. 
5. The bayou vegetation is similar to that of like areas along the 
stream, and only minor differences were brought out; but on com- 
paring this vegetation with that of the glacial lakes about Ann Arbor, 
the most pronounced differences were discovered when the respective 
swamp and bog societies were compared. Andromeda polifolia, 
Chamaedaphne calyculata, Arethusa bulbosa, Sarracenia purpurea, 
Oxycoccus macrocarpus, Drosera rotundifolia, and sphagnums are 
common about lakes, but absent or very rare along the stream. In 
both cases, however, there is a dominance of northern forms. 
2. FLOODPLAIN socrETIES.—The series of changes taking place 
in the previous group are continued until swamps and pools disappear, 
to be replaced by a dense woods of mixed mesophytic species. Three 
societies appear, often with a more or less zonal arrangement. 
(1) Moist sedge society.—Turf-forming grasses here make their 
first appearance, but are not able to replace entirely the terrestrial 
sedges, which occupy occasional areas. 
(2) Elm-ash-maple society—There is little space not occupied by 
tree growth, except where clearings have been made. Populus 
iremuloides and P. deltoides appear early as pioneers, followed later 
by Ulmus americana, U. pubescens, Fraxinus pennsylvanica, F. 
lanceolata, F. nigra, Acer saccharinum, A. rubrum, Platanus o0ce 
dentalis, and Tilia americana; which make up a woods character 
istically mixed, dense, and vine-clad. Of the herbaceous forms, 
only the most shade-enduring kinds with broad thin leaves are to be 
met with in the forest. Of these Urticastrum divaricatum, Acnida 
concatenaia, Adicea pumila, and Lobelia cardinalis are most — 
(3) Walnut society—The most abundant and characteristic tee 
of this association is Juglans nigra, which appears to have 
uniformly distributed, and often over three feet in diameter, * 
shown by stumps. It is one of the arboreal types which shows 5 
tendency to follow along streams or bodies of water. It a 
mixed with Juglans cinerea, Quercus macrocarpa, Hicoria re 
Quercus platanoides, and other species. It was attempted " “ 
acterize the group as a bur oak-walnut association. This 
