Figure 2-4. An aggregation 

 of the insectivorous pitcher- 

 plant (Sarracenia flava) in 

 a marsh in Louisiana. 

 (U.S.D.A. Soil Conservation 

 Service.) 



tion, germination, establishment (Figure 2-2), aggregation (Fig- 

 ures 2-3 and 2-4), competition and other coactions, reaction (Fig- 

 ure 2-5), and replacement. Migration can be by seed or by 

 vegetative parts, the former often requiring more exacting condi- 

 tions than the latter. Establishment or ecesis is considered accom- 

 plished when the plants are reproducing themselves, but many 

 seedlings never succeed. Seedlings and vegetative offshoots tend 

 to aggregate about the parents, and this leads to competition for 

 light or other requirements, but some plants need the shade of 

 others or the protection of shrubs from grazing in order to reach 

 maturity. Usually the plants with the greatest competitive capa- 

 city have the best chance for survival. Reactions such as shad- 

 mg often make the environment less suitable for the present 

 occupants of an area but more favorable for other species which 

 may invade and become established. These processes are occur- 

 ring continually in all plant groupings and in time lead to great 

 changes during the course of ecological succession. 



Figure 2-5. Sandreed {Cala- 

 movilfa gigantea) has 

 formed a stand by means of 

 the vigorous growth of rhi- 

 zomes, now reacting on the 

 habitat by stabilizing the 

 sand movement. October, 

 Woodward, Oklahoma. 

 (U.S.D.A. Soil Conservation 

 Service.) 



