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. R., “ Island Life,” pp. 305 — 307. 
t Engler, A., “ Entwicklungsgeschichte der Elorengebiete,” II.. p. 179, 
\ Ihering, II. von, “ Das neotropische Florengebiet,” p. 50, 
