‘ 
26 MISSISSIPPI STATE GEOLOGICAL SURVEY [Bull. 
Such a progressive and orderly series of changes is called 
a Forest Succession. But successions are not limited to forests, 
and may take place under very diverse conditions. One of the 
most interesting successions to observe is that which takes 
place in a filling lake, the different plant associations or for- 
mations following each other in successive zones from the 
edges to the centre of the lake basin. In clear lakes the central 
deep waters are occupied by floating aquatics, such as pond- 
weeds; surrounding this central deep, rooted in somewhat 
shallower water, with their leaves floating upon the surface, 
pond lilies and water-shield form a distinct zone; in still shal- 
lower water surrounding the lily zone, is a zone of bulrushes; 
beyond these in water but a few inches deep, is a zone of the 
tall cattail flag; in the oozy, muddy edges forming a fringe 
all around the pond, is a zone of sedges and coarse grasses; in 
the damp rich soil beyond the water’s edge, up the slopes, 
mesophytie herbaceous flowering plants occupy the ground, 
these followed in turn on higher ground by shrubs and trees 
oi the surrounding lands. 
As the lake slowly fills by sedimentation, and the addition 
of vegetable matter from the zonal growths, these associations 
cradually encroach upon the lake, the pondweed association 
disappearing firsi, teing replaed ‘vy the lily and water-shield 
formation; these as the shallowing goes on, are gradually 
crowded out by the next zone; and so on through the series 
of changes, until the lake is gradually obliterated, and the 
mesophytic vegetation of the adjacent lands occupies its site. 
In the above examples of successions, the first shows a 
progressive succession from comparatively xerophytie condi- 
tions to mesophytic conditions, since a pine forest is a xerophy- 
tic growth and a mixed forest of oak, hickory and other hard- 
wood tree and shrubs is distinctly mesophytiec. 
In the second example, that seen in the filling lake, the - 
