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Krakatao one d ) germinating spore of Pteris vittata -). The layer of 

 algae being permanently moist or at least drying out less than the soil 

 proper, spores may have germinated on it also in the east-monsoon 

 which, as I have already stated above, is interrupted by frequent 

 rains- But in all probability the presence of algae was not a conditio 

 sine qua non for the development of a fern-vegetation. Everywhere 

 in Java may be observed that fern-spores germinate quite well in 

 humid substrata not covered by algae and this may very well have 

 happened also in Krakatao, at least in the West-monsoon. Admitting 

 that perhaps the layer of algae has contributed to a large extent 

 to a rapid extension of the fern-flora I hold that it was not an 

 indispensable preparer of the locality. But by its presence spores 

 may have germinated throughout the year whilst otherwise perhaps 

 they could only have done so in the West-monsoon. The part taken 

 in the tropics by algae in facilitating the germination of fern-spores 

 should be further investigated. 



8. What would happen if Krakatao was situated at a very great 

 distance from every plant-covered land? The Phanerogams established 

 on the beach would ascend the mountain to a certain height driving 

 back before them the ferns. This movement would be arrested as 

 soon as the conditions above the height reached were unfit for littoral 

 plants. The seeds of other Phanerogams, fit to live at greater altit- 

 udes, would never or but very rarely reach the island, lost in the 

 ocean. Therefore in the higher part of the island the ferns, perhaps 

 accompanied by some Lycopods, would predominate for ever; the 

 Phanerogams would be restricted to the lower parts and the beach. 

 This supposed case is found realized in /uan Fernandez and 

 Ascension. The small volcanic island {uan Fernandez is situated at + 

 625 km. from the coast of Chili and Mose/ey says of the flora: There 

 ,,are upwards of 24 species of Ferns growing in tlys small island and in 

 ,,any general view the Ferns form a large proportion of the main mass 

 ,,of vegetation". The soil of Ascension, an entirely volcanic island of 

 about the same height as Krakatao, is described as follows: ,,St. 

 Helena has been called a barren rock, but it is a paradise as compared 

 ,,with Ascension which consists of a scorched mass of volcanic matter 



1 ) This _one spore apparently possessed the fission-power of a bacterium. In 

 W a r m i n g's Pflanzengeographie (3e Aufl. 688) it has already multiplied to: ,,Farnsporen 

 welche sich in Menge einfanden". 



2 ) The tetraedal spores of this fern are by the very prominent ridges they are 

 provided with easily distinguishable from the spores of the other ferns found by 

 Treub in Krakatao. 



