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 1 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 2 ." 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 3 ." 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 4 ." 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 5 ?" 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 Qp. cit. p. 72. 



* Op. cit. p. 56. 6 More Letters, i. p. 483. 



