220 



Docters van Leeuwen. Most mangrove-plants do require a deep, 

 muddy soil, but some species f.i. Sonneratia alba Smith, Rhizophora 

 sty/osa Griff., Rhizophora con/ugata L., Aegiceras cornicu/atum Ga'rtn. 

 and Avicennia marina Vierh. may thrive quite well on almost bare 

 rocks, provided these are daily exposed to the tide. Very many 

 ,,genuine beach-plants" on the contrary, among them numerous her- 

 baceous ones, do not content themselves with Comparatively bare 

 rocks" but require a rather deep soil, f.i. Albizzia retusa Bth. 

 Caesa/pinia crista L, Casuarina equisetifolia L. Dodonaea viscosa 

 /<jc<y. (the littoral form), Euphorbia atoto Forst., Hernandia pe/tata 

 Meissn, /osephinia itnperatricis Vent. Remirea mar it i ma Aubl. 

 Spinifex littoreus Merr. Tribulus cistoides L. Triumfetta repens Merr. 

 et Ro/fe, Vitex ovata Tfiunb. and many others. 



Mr. Docters van Leeuwen found somewhere on Verlaten 

 Liland one seedling of Cocos nucifera at a few yards' distance from 

 the sea, from which fact he concludes that this species can spread 

 independently of human aid. As it is not certain that the nut had been 

 carried there without any human aid and as moreover it is not at all sure 

 that the plant will survive, the seedling, even now that it has been 

 photographed and ,,this fact has been fixed", can hardly be considered 

 to have furnished the required proof. For such a proof much more 

 unimpeachable arguments are needed. At Zwarte Hoek in 1906 seed- 

 lings of this palm were seen, that proved to have disappeared in 

 1908; in 1908 other seedlings were observed that were not found 

 back in 1919. If the specimens of 1906 and 1908, whether planted or 

 not, were not able to maintain themselves, why should we assume 

 beforehand that the single young seedling of 1919 will be fit to do so. 

 As the exact habitat of the photographed specimen is not indicated, 

 it will be impossible for future investigators to locate it with cer- 

 tainty; it can perhaps not be found back. 



For the speculations on the introduction of seeds and fruits in 

 the intestines of birds, I refer to p. 13 and p. 71. As to import of seeds 

 attached to the feathers of birds or carried over by wind, such seeds 

 seem not yet to have been observed on Krakatao. The plants 

 supposed to be issued from them lead, for the present, only an 

 easy theoretical life on paper, not a more difficult real one in 

 Nature. 



10. In this paragraph Mr. Docters van Leeuwen gives an excerpt of Treubs 

 paper on Krakatao, whose opinions as to the complete destruction of the old 

 flora and the mode of introduction and development of the new one he fully 



