Initial Stages in Colonisation 5 



I. Results of the visits of 1886 and 1897. 



Dr Melchior Treub, the distinguished and genial Director of the 

 Botanical Institute at Buitenzorg in Java, rendered a great service to 

 Science by initiating the study of the new Krakatau flora and thus 

 paving the way for further investigations. The botanical explorations, 

 made on three different occasions, of the islands which were entirely 

 depleted of vegetation in Itttt'A have not only furnished results of 

 general biological interest, but by demonstrating the successive 

 stages in colonisation, they also afford one of the most important 

 contributions towards the solution of the much discussed problem as 

 to the source and history of the introduction of a flora into an island 

 far removed from the mainland. The older literature 1 concerned 

 with this interesting problem in plant-geography, so far as regards 

 direct observation, deals with the history of colonisation of recently 

 formed coral islands, that is of flat land surfaces, and with the 

 investigation of the means of dispersal of plants from older coral 

 reefs and volcanic islands. On Krakatau, Treub 2 had an opportunity 

 of studying the more complex problem : how a volcanic island, which 

 has lost the whole of its flora as the result of an eruption, acquires a 

 new vegetation ; how, in other words, an island of considerable height 

 suddenly emerging from the sea becomes stocked with plants ; and 

 further by what successive stages the new floral elements appear on 

 the island and by what external agencies the colonisation is effected. 



The first germs of land-plants are brought by ocean-currents 

 which carry seeds and fruits, drifting on the surface of the water, to 

 the low-lying beach of emerging coral islands. Some of these seeds 

 on arrival are still capable of living ; they germinate and, provided 

 the conditions are not too unfavourable, continue to grow and con- 

 stitute the first plants of the island. It has long been known that 

 only a comparatively small proportion of plants are capable of ex- 

 tending the area of their distribution by this means. 



A comparison of island floras has shown that it is exclusively 

 strand-plants in the Malay Archipelago there are about 320 species 

 which have seeds and fruits possessing the necessary adaptations for 

 this method of dispersal by ocean-currents, that is which are capable 



1 A complete list will be found in W. B. Hemsley's "Report on the present state of 

 knowledge of various Insular Floras." Introduction to the first three Parts of the 

 Botany of the Challenger Expedition, Botany, Vol. i. p. 69. 



2 M. Treub. "Notice sur la nouvelle Flore de Krakatau." Annates du Jar din 

 botanique de Buitenzorg, Vol. vil. 1888. 



M. Treub. "Overhet nieuwe Plantenkleed van Krakatau." Natuurkundig Tijd- 

 schrift root' Nederlandsch- Indie, Band 48, 1889. 



