32 



very humid localities. These were probably 1 ) collected in deeply 

 eroded ravines, where the water-table was very high. Of the 9 other 

 ones (see in chapter IV the corrected list of Treub's finds) no 

 less than 7 belong to the just-mentioned kremnophytes. 



This, anew, points to the possibility that the rich fern-flora found 

 by Treub on Krakatao within 3 years after the eruption and 

 wich may have been present much earlier was not introduced from 

 without hut originated from the island itself. \ admit that this is not 

 proven and that it never can be so, but the contrary is just as little 

 proven. That the rich fern-flora, found by Treub, originated from 

 surviving specimens of such ferns as may have grown for years on 

 the rocks, is much more probable than that in the period of not yet 

 fully 3 years between the visit of Verbeek and that of Treub, 

 spores were carried over by the wind from far across the sea in 

 such numbers that a rich and entirely new fern-vegetation could 

 arise. It is quite possible that within a few years the kremnophytic 

 vegetation was restored from its rests, that afterwards it extended 

 from there on localities as yet covered with ashes but, on the 

 rocks, remained as it was. Hence, Penzig in 1897 found 7 ,zum 

 grossten Teile noch unverandert dasselbe Vegetationsbild welches 

 Treub auf seinem ersten Besuche vor mehr als zehn Jahre antraf 2 )." 

 During the expeditions of 1906, 1908 and 1919 3 ) the base of the 

 basaltic rocks of Zwarte lloek still bore a very scanty vegetation; 

 nothing is known of the vegetation of the higher parts. 



Treub himself, without being aware of it, gave a very clear 

 hint to the possibility of the survival of part of the old flora. He says 

 that during his visit to Krakatao the other two islands of the group 

 did not bear any vegetation. Though he did not visit, much less 

 search these islands, and consequently had no right of speaking so 

 decidedly, it is sure, that, if they bore a new vegetation, this was 

 much less developed than that of Krakatao, otherwise Treub would 

 have seen it from his small ship that could and we may safely 

 suppose did sufficiently approach the shore. 



The fact that on the other two islands of the Krakatao-group 

 in 1886 a new vegetation was absent or, at least, was so little 

 developed as to be invisible from a slight distance, can be hardly 



1 ) Treub does not give any data about the habitat and f regency of the indi- 

 vidual species. 



2) Ann. |ard. Bot. Buitenzorg XVIII, p. 100. This communication probably originated 

 from Ireub who accompanie_cL Pen z i g. 



3 ) Docters van Leeuwen in Handelingen Eerste Ned. Ind. Natuurw. Congres 

 (1920), p. 42. 



