464 A TEXTBOOK OF GENERAL BOTANY 
Thus, there is a series of successions between the deeply sub- 
merged bare ground and the climax forest. 
Rocks may support only a growth of lichens, but as the rock 
weathers and soil accumulates there is a series of invasions which 
ends with the climax forest. 
On tropical coasts, mud flats are occupied by mangrove-swamp 
forest, but as the land is raised this is succeeded by the forest 
of the dry land and finally by the climax type of the region. 
The types of plant successions are very varied, are due to a 
great variety of local conditions, and lead to many types of 
climax vegetation. A study of successions shows that vegeta- 
tion is not static but dynamic, and that much of it is unstable 
and changing. Just as an individual passes through many stages 
of development before reaching maturity, so plant communities 
go through various stages, or successions, before the climax type 
is produced. . 
