The New Flora of Krakatau 317 
PostscRIPTUM. 
Since this essay was put in type Dr Ernst’s striking account of 
the New Flora of the Volcanic Island of Krakatau' has reached 
me. All botanists must feel a debt of gratitude to Prof. Seward for 
his admirable translation of a memoir which in its original form is 
practically unprocurable and to the liberality of the Cambridge 
University Press for its publication. In the preceding pages I 
have traced the laborious research by which the methods of Plant 
Dispersal were established by Darwin. In the island of Krakatau 
nature has supplied a crucial experiment which, if it had occurred 
earlier, would have at once secured conviction of their efficiency. 
A quarter of a century ago every trace of organic life in the island 
was “destroyed and buried under a thick covering of glowing stones.” 
Now, it is “again covered with a mantle of green, the growth being 
in places so luxuriant that it is necessary to cut one’s way laboriously 
through the vegetation”.” Ernst traces minutely how this has been 
brought about by the combined action of wind, birds and sea currents, 
as means of transport. The process will continue, and he concludes :— 
“ At last after a long interval the vegetation on the desolated island 
will again acquire that wealth of variety and luxuriance which we 
see in the fullest development which Nature has reached in the 
primaeval forest in the tropics®.” The possibility of such a result 
revealed itself to the insight of Darwin with little encouragement 
or support from contemporary opinion. 
One of the most remarkable facts established by Ernst is that 
this has not been accomplished by the transport of seeds alone. 
“Tree stems and branches played an important part in the coloni- 
sation of Krakatau by plants and animals. Large piles of floating 
trees, stems, branches and bamboos are met with everywhere on the 
beach above high-water mark and often carried a considerable 
distance inland. Some of the animals on the island, such as the 
fat Iguana (Varanus salvator) which suns itself in the beds of 
streams, may have travelled on floating wood, possibly also the 
ancestors of the numerous ants, but certainly plants‘.” Darwin 
actually had a prevision of this. Writing to Hooker he says :— 
“Would it not be a prodigy if an unstocked island did not in the 
course of ages receive colonists from coasts whence the currents 
flow, trees are drifted and birds are driven by gales®?” And ten 
years earlier :—“I must believe in the...whole plant or branch being 
washed into the sea; with floods and slips and earthquakes ; this 
1 Cambridge, 1909. 2 Op. cit. p. 4. 3 Op. cit. p. 72. 
4 Op. cit. p. 56. 5 More Letters, 1. p. 483. 
