73 



the east and south side of Krakatao were preceded by a vegetation 

 of ferns. Higher plants may quite well have been among the first 

 to appear. Nothing thereabout is known. 



6. It is not at a/I strange that numerous fern-spores drop on 

 Krakatao as even the seeds of Phanerogams are carried over by wind. 

 But it is a/most inconceivable how ferns and their protha/lia can live 

 in the very arid soil of Krakatao which is a/most continually heated 

 by the glowing sun, whilst there is not the least shadow, Treub and 

 Burck have in the laboratory at Buitenzorg sowed spores from Krakatao 

 on many different substrata in order to ascertain whether the prothallia 

 and seed/ings of these ferns possess special adaptations enabling them 

 to live in such unfavourable circumstances as presented by Krakatao. 

 No such adaptations could be found. 



My views on the first part of this conclusion have already been 

 stated herebefore (pp. 64, 65). The basaltic rocks investigated by 

 Treub were doubtless very unfertile. But, as Ernst 1 ) rightly obs- 

 erved, the pumice- and ash-fields were by no means so poor as 

 Treub thought. The ashes contained in soluble compounds nearly 

 all salts indispensible for plant-growth and in sufficient quantities, 

 barring nitrogen- and phosphor-compounds. Nitrogen-compounds could 

 be supplied by water, either falling as rain which in the tropics often 

 carries down much dust which was floating in the air, or flowing down 

 the ravines during heavy showers. Such higher parts of the ravines as 

 were already laid bare or almost so must have contained many easily 

 removable organic or anorganic rests of the former vegetation; water 

 containing nitrogen-compounds could reach the upper layers of the soil 

 by capillary motion. To my knowledge no analysis has been made of 

 the ground-water of Krakatao. But a well, sunk in 1896 on Lang Eiland, 

 which island was in much the same circumstances as the lower ash- 

 and pumice-fields of Krakatao, yielded water undrinkable on account 

 of its high percentage of organic substances 2 ). Ernst, moreover, 

 draws attention to the animal and vegetable rests which were washed 

 ashore, part of which might be driven into the interior by wind. 

 Treub did not institute an investigation after the presence of soil 

 bacteria, fixing free nitrogen. Hence one cannot ascertain to which 

 degree by such bacteria the growth of higher plants in 1886 was 

 promoted or made possible. But it is very probable that the nitrogen 



!) Ernst, Neue Flora Vulkaninsel Krakatau (1907), p. 51. 



2 ) Tiidschr. Koninkl. Ned. Aardr. Genootschap XIV (1897), p. 120. 



