392 ORIGIN OF LIFE IN AMERICA 



and other countries. Dr. Wallace,* however, acknowledges 

 that specific identity among ferns does not necessarily imply 

 a recent origin. According to Professor Engler f the five 

 endemic genera are somewhat related to American ones, 

 whereas some species of Pelargonium, Mesembryanthemum, 

 Wahlenbergia and Oteospermum must have originated in 

 Africa. 



Dr. von Ihering J discusses all the various modes of dis- 

 persal, by birds, winds and ocean currents, in connection 

 with the origin of the flora of St. Helena, and rejects them 

 as quite inefficient. In his opinion, only a land connection 

 with Africa and South. America could have produced the flora. 



Although St. Helena is surrounded by great ocean depths, 

 and possesses neither mammals, reptiles nor amphibians, we 

 cannot assume, as Dr. Wallace has done, that the whole fauna 

 and flora owe their origin to accidental dispersal by birds, 

 winds and ocean currents. If such were the case, there is no 

 reason why these modes of transport should not have been 

 equally effective in Pliocene and Pleistocene times than in the 

 older geological periods, and why there should not be many 

 species differing but slightly from American or African ones. 

 Everything, on the other hand, points to the animals and 

 plants being almost all of extreme antiquity. We have either to 

 suppose, therefore, that during some very remote period the 

 modes of transport alluded to were far more efficient than they 

 are now, or that St. Helena was connected by land with South 

 America and Africa. For many reasons, already fully dis- 

 cussed in this chapter, the latter hypothesis appears to me 

 the only one that is at all probable. If we assume that there 

 was such a land bridge, it is quite possible that the actual 

 volcanic area now forming St. Helena was not in existence, 

 but originated after portions of the land connection had 

 already subsided. A mere remnant of the fauna and flora 

 would eventually have taken refuge on the rock of St. Helena, 

 whilst the surrounding country disappeared beneath the 

 floods. Whether in early Tertiary, or even in later Tertiary 

 times, there was a short and independent land bridge between 



* Wallace, A. E., " Island Life," pp. 305307. 



t Engler, A., " Entwicklungsgeschichte der Florengebiete," II., p. 179. 



| Ihering, H. von, " Das neotropische Florengebiet," p. 50. 



