60 Means of Dispersal 



dispersal of their seeds by fruit-eating doves. Penzig 1 has demonstrated 

 the introduction of Melastoma polycmthwm by bird-agency. Among 

 the latest arrivals on the island there is no doubt that Trema 

 amboinensis, one of the Celtidoideae with small juicy fruits, must be 

 included in the list of plants introduced by animal-agency. Carica 

 Papaya, which occurs on Verlaten island, in addition to its dispersal 

 by birds may also be carried by flying foxes (Pteropus) which, according 

 to statements by Forbes (Joe. cit. p. 34), are capable of extended flight 

 over water. As already pointed out, the fact that Verlaten island was 

 inhabited for a short time some years ago renders it possible that this 

 favourite plant in cultivation was introduced by man. 



3. Dispersal of fruits and seeds by wind. 



The third method of dispersal of fruits and seeds, by wind, is of 

 exceptional importance as a factor in the development of the new 

 flora of Krakatau. This was demonstrated in a remarkable way 

 during Treub's first visit to the island. Previous to the publication 

 of the results of the first Krakatau expedition of 1886, opinions in 

 regard to the part played by wind in the colonisation of new land, 

 especially in the case of distant islands, were divided 2 . The view was 

 widely held that the dissemination of spores and seeds by air-currents 

 was only of local importance, and only assumed a geographical 

 significance after frequent repetitions in the course of generations. 

 This opinion was based on many observations on the colonisation 

 of freshly exposed surfaces on the mainland where ground had 

 been either partially or completely deprived of vegetation and 

 afterwards colonised from neighbouring districts. Patches of new 

 ground may be formed by earthquakes, floods, the accumulation of 

 detritus-cones, piles of boulders, glacial moraines in the mountains, 

 sandbanks in river-beds and at the mouth of rivers and by the 

 formation of lava- and ash-fields in volcanoes. Seeing that the action 

 of wind as a factor in the dispersal of vascular plants 3 falls behind 

 other agents of distribution when the newly exposed land is com- 



1 Penzig, 0., loc. cit. p. 111. 



2 Vide Schimper, A. F. W. Pflanzengeographie, 1898, p. 90. [Plant Geography, 

 p. 80.] 



3 In the Alps, where disturbances in the surface of the ground occur much more 

 frequently than in the plains, the anemochoric species (that is, those which owe their 

 seed-dispersal to wind) predominate; Vogler ["Uber die Verbreitungsmittel der 

 schweizerischen Alpenpflanzen," Flora, Bd. 89, 1901, p. 73 (Reprint)] has supplied a 

 particularly good example of this, supported by statistics, in his account of the 

 spread of vegetation over the ground which was left bare by the shrinkage of the 

 Rhone glacier. 



