Vegetation in 1886 7 



the ravines on the mountain slopes. Investigations made during 

 subsequent expeditions demonstrated the association of Diatoms and 

 Bacteria with the blue-green Algae. The dark green gelatinous 

 layer with which these minute, self-sufficient, and doubtless wind- 

 borne organisms covered the pumice and ash formed a favourable 

 nidus for the germination of the spores of mosses and ferns and of 

 the seeds of such phanerogams as are adapted by their small size 

 and weight to dispersal by air-currents. An especially characteristic 

 feature of the first stage of colonisation was the preponderance of ferns, 

 which were represented by 1 1 species widely spread in the Indo-Malay 

 Archipelago ; only two of these, however, belong to the strand-flora of 

 the islands. 



In addition to cryptogams phanerogams were also met with on 

 the island in 1880, though in comparison with ferns they were at first 

 represented by a relatively small number of species and individuals. 

 In the Drift-zone of the beach, Treub found seedlings of nine species 

 of phanerogamous plants, the seeds of which had germinated on being 

 washed up by the sea, also the fruits and seeds of seven other 

 phanerogams which, like the former, belong to the strand vegetation 

 characteristic of the Malay Archipelago. In the interior and on the 

 slopes of Rakata, the number of phanerogams amounted to eight 

 species, two of which were identical with those found on the beach. 

 The remaining six species, four Compositae and two grasses, plants 

 with light fruits some of which were provided with special adapta- 

 tions to wind-dispersal were obviously, like the minute spores of 

 the cryptogams, transported by air-currents from the neighbouring 

 islands to the new land surface of Krakatau. Plants introduced by 

 animals or man were not found on the uninhabited and barely 

 accessible island. 



The problem of the colonisation or re-stocking of a high volcanic 

 island situated far from the mainland was thus solved in a remark- 

 able manner by Treub's researches. It was demonstrated that the 

 elements of the strand-flora played a very subordinate part in the 

 composition of the new flora, a result entirely contrary to what one 

 would expect from the analogy of coral islands Avhere these elements 

 are the first colonists. The flora of the interior of the island had 

 developed not only independently of the strand-flora but also with 

 much greater rapidity : the number of species was greater and in the 

 case of certain ferns the number of plants was sufficiently large to 

 constitute a characteristic feature in the general facies of the 

 vegetation. A few phanerogams were first met with as isolated 

 plants among the ferns botli on the mountain and on the beach. 



To follow the gradual changes in this new plant-world of the 

 island, poor in species and brought together in so remarkable a 



