LAWS 135 



(3) Grassland or forest is the usual terminus of a suc- 

 cession : they predominate in lands physiographically 

 mature. 



(4) The limit of a succession is determined in large part 

 by the progressive increase in occupation, which 

 makes the entrance of invaders more and more diffi- 

 cult. 



(5) Stabilisation proceeds radiately from the pioneer 

 plants or masses. The movement of offshoots is 

 away from the parent mass, and the chances of ecesis 

 are greatest near its edges, in a narrow area in which 

 the reaction is still felt, and the occupation is not 

 exclusive. 



VL General Laws. 



(1) The stages, or formations, of a succession are dis- 

 tinguished as initial {prodophytia), intermediate 

 [ptenophytia), and ultimate (aiphytia). 



(2) Initial formations are open, ultimate formations are 

 closed. 



(3) The number of species is small in the initial stages. 

 It attains a maximum in intermediate stages, and 

 again decreases in the ultimate formation, on ac- 

 count of the dominance of a few species. 



(4) The normal sequence of vegetation forms in suc- 

 cession is: (1) algae, fungi, mosses; (2) annuals and 

 biennials; (3) perennial herbs; (4) bushes and 

 shrubs; (5) trees. 



(5) The number of species and of individuals in each 

 stage increases constantly up to a maximum, after 

 which it gradually decreases before the forms of the 

 next stage. The interval between two maxima is 

 occupied by a mixed formation. 



(6) A secondary succession does not begin with the in- 



itial stage of the primary one which it replaces, but 

 usually at a much later stage 



(7) At present, successions are generally mesotropic, 

 grassland and forest being the ultimate stages, 

 though many are xerostatic or hydrostatic. If 



