THE FLORA OF THE COAST ISLANDS. 519 



dying out. They have been mostly destroyed and replaced 

 by newer and stronger forms. I conclude, therefore, that 

 in Pliocene times several species of Lavatera existed all over 

 the coast region of California, but probably mostly in the 

 then coast range, viz: the islands; for they love the sea 

 coast. They have all been destroyed by change of environ- 

 ment, physical and organic, except those isolated on the 

 islands and thus saved from the effects of invasion. 



Eeaders of Mr. Wallace's ''Island Life" will at once see 

 the analogy between this explanation of the flora of ou- 

 coast islands and Mr. Wallace's explanation of the mamma 

 lian fauna of Madagascar. The mammalian fauna of Africa, 

 south of Sahara, consists of two very distinct groups — the 

 one indigenous or descendents of Tertiary indigenes, and 

 remotely resembling that of Madagascar, the other evidently 

 foreign and resembling that of Eurasia in 3Iiocene and Plio- 

 cene times. During Tertiary times Africa was isolated 

 from Eurasia, but united with Madagascar, and the 

 whole inhabited by a peculiar fauna, characterized by 

 lemurs, insectivores, etc., which we have called indigenes. 

 About middle Tertiary times, Madagascar was separated, 

 and immediately divergence between the two faunas com- 

 menced. In later Tertiary and early Quaternary, the 

 barrier which separated Africa from Eurasia was removed, 

 and the great Eurasian animals invaded Africa, and imme- 

 diately became the dominant type. In the struggle which 

 ensued, many species, especially of tlie weaker indigenes, 

 were destroyed, and all on both sides modified. The result 

 is the African fauna of to-day. Madagascar was saved from 

 this invasion by isolation. The fauna there consists of the 

 greatly modified descendants of the African Tertiary indi- 

 genes, but far less modified than their congeners in Africa. 

 In the fauna of Madagascar, therefore, we have the nearest 

 approach to the Tertiary indigenes of both. 



The difference between the two cases is this : In the case 

 of Madagascar the separation has been very long. The 



