70 Formation of Plant-Associations 



crabs most eagerly search for and which can least withstand their 

 attacks. 



The level ground behind the strand-forest, gently sloping towards 

 the foot of the cone, as well as the lowest ridges and valleys of the 

 mountain, are still occupied as they were ten years ago chiefly by 

 Grasses, Cyperaceae and Compositae, while the Ferns have already come 

 to occupy a subordinate place. Two representatives of the phanerogams 

 of the shore (Scaevola Koenigit and Tournefortia argentea) were 

 found by Treub in the interior. Since then the trees and shrubs have 

 increased in number in the steppe or desert-like regions. These have 

 advanced either singly or in groups on to the flat ground beyond the 

 strand-forest and, as we have already described, they have formed 

 forest-like patches in the ravines of the cone. 



If the further development of the present Krakatau vegetation is 

 not interrupted by a fresh volcanic outburst, the island, with the 

 exception of the steep rock-face, may be completely clothed with 

 vegetation in the course of the next fifty or sixty years. 



The volcano of Tamboro in the island of Sumbawa has become 

 covered afresh with a dense forest within a similar period. In the 

 shore-zone the extension of the forest-formation will lead to the 

 disappearance of clearings which are occupied by herbaceous plants 

 and bushes. During the development of a closed Barringtonia 

 formation, some of the present members of this association will in 

 the future have a difficult task in competing with the growth of 

 new species. The building up and completion of the formation 

 will, as elsewhere, be accompanied by a reduction in the number 

 of species. Less well equipped forms will disappear or will be 

 driven towards the shore, where they will mix with plants of the 

 Pes-caprae formation and in some places oust them from their 

 position. Low or slow-growing trees and shrubs which can no longer 

 flourish in the high Barringtonia forest may spread inland almost 

 unhindered. Those plants which have hitherto been facultative 

 strand species, possessing seeds or fruits which, though not definitely 

 wind-borne, may be carried inland by wind for short distances, will 

 rapidly spread towards the interior ; similarly other plants, as, for 

 example, the different species of Ficus, the fruits of which are readily 

 eaten by birds, will spread in the same direction. It is possible that 

 the forest in the principal gorge of the mountain is at present com- 

 posed of these elements of the coast-flora ; perhaps future visitors to 

 the island may find there many other plants, the germs of which have 

 been introduced by birds, but more especially by wind, from the 

 neighbouring islands and not from the littoral zone of Krakatau. 

 We may indeed expect that plants will eventually be found in the 



