169 



which may have been rightly recorded by Ernst for this side of 

 the island. On the other hand 3 littoral species not observed on the 

 south-eastern side were collected at Zwarte Hoek, viz. Pithecolobium 

 umbe/latum Bth. (20) *), - Dem's heterophylla Backer (23) and Ccrbera 

 manghas L. (34\ This proves how dangerous it is to conclude from 

 the investigation of a part of the beach, that a littoral species is 

 absent from the entire island, and 1 cannot at all agree with Ernst 

 who apparently considers all species observed for the first time 

 in 1906 on Krakatao as ,,in den letzten 10 Jahren eingewanderte 

 ,,Arten" 2 ). All of these species may have occurred on Krakatao 

 already long before 1897. 



The typical littoral species and halophytes were most probably in- 

 troduced after the eruption, but the same cannot be said of the flora 

 of the interior, the total destruction of which in 1883 is not in the 

 least proven. The vegetation of the lower parts of the slopes of 

 Krakatao, like that of all localities clothed with an undisturbed young 

 vegetation in moist regions of the tropics, has certainly in the course 

 of years much changed. But we do not in the least know whether 

 the ,,new" plants found in 1906 on these slopes were new for the 

 island itself or had come over from other parts of it. All that has 

 been said about the flora of the interior between 1886 and 1906 

 having grown richer, and on the mode of introduction of the so- 

 called new inland species are mere guesses without scientific value. 



I shall shortly discuss the species found on Krakatao for the first 

 time in 1905 or 1906. Soil-bacteria (No. 1-3 and 5 of list D) proved 

 to be as copious as in Buitenzorg. It is fully unknown when they 

 have first appeared in the investigated localities. It has been often 

 alleged but was never proven that the island was quite sterilized by 

 the eruption of 1883. I think it quite possible, even very probable, 

 that in the higher ravines of the island which had been covered only 

 with a thin and not very hot layer of ashes and grit, a number of 

 bacteria have survived the eruption and from there have gradually 

 spread over the thickly and permanently covered lower parts. Of 

 course introduction from without the island can also have taken 

 place. Attention should be paid to the new aerobic free-living 

 nitrogen-fixing Bacterium Krakataui which was found in the Casuarina- 

 grove and in the Pes-caprae-formation and to Bacillus radicicola, the 

 common bacterium of the nitrogen-tubercles on the roots of Legumi- 



1 ) The numbers between brackets refer to list A herebefore. 



2 ) Ernst, Neue Flora Vulkaninsel Krakatau (1907), 46. 



