VON IHERING'S RESEARCHES 



383 



tinct. All the more modern families of these continents show 

 scarcely any traces of relationship to one another. Conse- 

 quently we must conclude with Dr. Ortmann and several other 

 authors who have definitely expressed themselves on the geo- 

 logical age of the former land bridge between South America 

 and Africa, that the latter ceased to exist before Tertiary 

 times. 



Dr. von Ihering* did not limit his studies in South America 

 to the fauna, he likewise urged, contrary to the opinion 

 held by most botanists, that the floras of South America and 

 Africa pointed unmistakably to the existence of his " Arch- 

 helenis." His arguments were so convincing that Professor 

 Englerf adopted his views after a very careful and critical 

 examination of the problem from a botanical aspect. He ac- 

 knowledged that for a long time he had looked upon the theory 

 of a former land connection between South America and Africa 

 with scepticism, chiefly on account of the great intervening 

 ocean depths and the marked endemism in the flora of the two 

 continents. After discussing the various means of accidental 

 dispersal, and eliminating those plants which might possibly 

 owe their presence in both continents to some of the known 

 modes of occasional transport, he was impressed by the cir- 

 cumstance that there was still a residuum of species, genera 

 and families which must have had another origin. He urged 

 that the distribution of the Strelitzioidae, whose fruits cannot 

 be dispersed by wind, also that of some of the water plants of 

 Africa, which have very near relations in South America, and 

 others might be accounted for by the supposition of the former 

 existence of a series of large islands in the Atlantic Ocean 

 separated by narrow channels. All the same he prefers a 

 complete land bridge between the two continents. 



Dr. Ajrldt J discusses the problem in a very effectual manner 

 both from a biological and a geological point of view. Like 

 Dr. Ameghino, however, he is led to the conclusion that even 

 in early Tertiary times South America was still directly joined 



* Ihering, H. von, " Das Neotropische Florengebiet." 

 t Engler, A., " Floristische Verwandtschaft zwischen Afrika and 

 Amerika," pp. 50 51. 



| Arldt, Th., " Entwicklung der Kontinente," p. 451. 



