116 SUCCESSION 



sippi delta, where its effects are merged with the paludation 

 of tidal rivers, and the wave and tide erosion of the sea 

 shore. Such successions are unique in as much as the 

 denuding force operates very slowly instead of quickly, and 

 the first pioneers of the new vegetation appear before the 

 original formation has been destroyed. In all cases, the 

 succession is from mesophytic or halophytic formations to 

 paludose, and, finally, marine vegetation. In small areas of 

 subsidence, such as shore slips along lakes and streams, 

 sink holes and sunken bogs, the succession is usually both 

 short and simple, mesophytes giving place to amphibious 

 and ultimately to aquatic forms. 



11. Succession in landslips. Landslips occur 

 only in montane and hilly regions, and here they are 

 merely of local importance. In many respects, they are not 

 unlike talus: they show essential differences, however, in 

 that they are not sorted by gravity, and in that they destroy 

 vegetation almost instantly. The succession arises as a 

 rale, not upon the original soil, but upon that of the land- 

 slip, and, as pointed out elsewhere, might well be regarded 

 as primary. 



12. Succession in drained, or dried soils. 

 In geological times, the subsidence of barriers must often 

 have produced drainage and drying-out, ]ust as elevation 

 frequently resulted in flooding and lake formation. At the 

 present time, the drying-out of lakes and ponds is the result 

 of artificial drainage, or of climatic changes. The former 

 will be considered under successions brought about by the 

 agency of man. Climatic changes when general operate so 

 slowly that the stages of such successions are perceptible 

 only when recorded in strata. More locally, climate swings 

 back and forth through a period of years, with the result 

 that in dry years the swamps and ponds of wetter seasons 

 are dried out, and the vegetation destroyed or changed. If 

 the process be gradual, the succession passes from hydro- 

 phytic through amphibious to mesophytic, and, in dry 

 regions, xerophytic conditions : when the process of drying 

 out occurs rapidly, as in a single summer, the original for- 



