Means of Dispersal 67 



introduction on floating wood, on pieces of drifted pumice carrying 

 sand and seed, while some of the plants may have been introduced by 

 birds. Of the total number of phanerogams found on the group of 

 islands up to 1 906, 36 (39%) have certainly been brought by ocean- 

 currents. If we include such Krakatau strand-plants as belong to 

 genera with well-known halophytic species and such typical strand- 

 plants as may possibly have been distributed by birds, together with 

 strand species of Compositae, Grasses and Cyperaceae, which may 

 have been introduced by sea-currents as well as by wind and birds, 

 the number of plants included in this group is brought up to 67, or 

 72 % of the total. 



The number of plants brought to the islands by birds cannot be 

 exactly estimated. It is almost certain that the nine inland species 

 (10 % f the total) mentioned on page 58 and possibly nine species 

 in the list of strand-plants were introduced by this means, that is 18 

 species in all or 19 % of the whole flora; this estimate does not take 

 account of the possible part played by marsh and water birds in the 

 dispersal of Grasses and Cyperaceae. 



The data in regard to the number of wind-distributed species are 

 equally doubtful. If we include only the Orchidaceae, the Gramineae, 

 with the exception of Spinifex and Ischaemum, also Mariscus 

 iimbellatus among the Cyperaceae, and excluding all the Composites 

 which occur on the strand, the number amounts to 15 species or 

 16 % j including all the Composites and the four Cyperaceae, 

 28 species or 30% of the total. 



The facts given in the list of the Krakatau flora in regard to the 

 distribution of individual plants show that they are almost without 

 exception species which are ubiquitous in the tropical zone or at all 

 events in the Malay Archipelago. Any attempt to explain the 

 occurrence of the few species which are not widely distributed, by 

 reference to the prevailing currents and winds from Java, Sumatra, 

 and the other islands of the Archipelago, must for the present at 

 least prove futile. This is due to the fact that the floras of the 

 different localities in Java and Sumatra with which we are concerned 

 and of the other islands in the Java Sea and Sunda Strait are too 

 little known. 



Of the total number of phanerogams, according to the method of 

 reckoning adopted, 39 72 % have been introduced by sea-currents, 

 10 19% by birds, and 16 30 % by air-currents. In order to 

 appreciate correctly the importance of the dispersal of germs by wind- 

 agency it is necessary to bear in mind that the Ferns, of which there 

 are 16 species, also the lower cryptogams, almost without exception 

 (see Polystictus, p. 56) were introduced by this means. Wind- 



