288 SAGACITY AND MORALITY OF PLANTS. 



had moved farther south, and we accordingly find 

 them now forming part of the flora of South Africa, 

 and Brazil, etc., such as the Proteacece — the flora 

 occupying the low lands, which were first submerged 

 during a change of level, would be forced to retire 

 farther inland, and grow at higher elevations. In 

 both such cases as these there would be a tendency 

 to overcrowd the surface of the dry land, and to 

 cause a keener struggle for existence, resulting in 

 the extinction of some kinds, and the complete 

 alteration of others, under the influence of natural 

 selection. 



Large islands and parts of continental areas 

 have been broken up, by changes of level, into small 

 islands. These would still retain some of the old 

 plants of the mainland, whose altered surroundings 

 would have to be responded to in changed and 

 adapted structures. 



Suppose such a geological change to take place 

 when the climate was very warm — all the plants on 

 the newly-formed islands would then necessarily be 

 warmth -loving. If a climatal change occurred, the 

 increased cold would not go so hardly with the island 

 plants as with those of the adjacent mainland, 

 because an island climate is always more regular 

 and warmer than the continental climate in the same 

 latitude. So that whilst the plants on the latter 

 would change, or their places would be taken by 

 cold -loving plants from higher latitudes, those on 



