77 



,,/Vi part resembling bottle-glass and in part cokes and cinders". Hooker 

 says of the flora: A small green peak, 2800 feet above the sea, 

 monopolises a/I the vegetation, which consists of Purslane, a grass and 

 an Euphorbia in the lower parts of the is/and, whilst the green peak 

 is clothed with a carpet of ferns and here and there a shrub. Treub 

 mentioned these facts in order to show that the situation found by him 

 on Krakatuo forms no exception. 



This conclusion and the instances cited show that Treub did 

 not sufficiently take into account the innumerable factors by which a 

 vegetation is defined. It is here not the place to discuss the problem 

 of the vegetation of these and other islands but it is by far not 

 so simple as Treub supposed. Rainfall, evaporation, temperature, 

 soil conditions, origin and history of the flora, influence of man and 

 of the fauna have i.a. to be taken in account. Climatic conditions 

 are almost neglected by Treub and, as regards the instances cited, 

 also character and age of the vegetation, lie reckons only with intro- 

 duction from without, all other factors are dispensed with. 



Apparently 1 r e u b was of opinion that the sea washed ashore 

 almost exclusively seeds of littoral plants. Everyone who takes the 

 trouble to minutely examine the drift-zone will soon arrive at another 

 conclusion. In the list of drift-seeds given by Sc lumper ') 4 species 

 [Canarium, Chydenanthus (Barrinytonia) excc/sa, Paiigiu/n edu/e, Cyno- 

 metra cau/if/ora] are mentioned, which are no littoral plants. Of the 

 22 species of seeds and fruits (Cf. chapter VI) which P e n z i g in 

 1897 found washed ashore at Zwarte 1 lock 9 did not originate from 

 beach-plants. I hese seeds and fruits were too large for being driven 

 by the wind into the interior. Such large seeds and fruits most easily 

 strike the eye. But whoever has acquainted himself personally with 

 the drift-zone will admit that the rubbish washed ashore may contain 

 many small light seeds '-) which easily escape the eye of the untrained 

 investigator and may be driven by the wind into the interior to give 

 rise there to a new vegetation. The many factors promoting or 

 hindering the origin of such a vegetation cannot be discussed here. 

 That abundance of ferns need not be the result of the large distance 

 at which an island is situated from a plant-covered locality, is suf- 

 ficiently shown by the fact that in Java the mountain-rainforests 

 between I OCX) and 2500m. possess an extremely rich fern- vegetation. 

 Constant moisture is of infinitely more importance than distance. 



!) Sc him per, Indo-Malayische Strandflora (1891), pp. 101, 162. 

 -) Cf. p. 46, footnote 1. 



