173 



are either survivors of the old vegetation or were introduced after 

 the eruption. If the last be the case, one is inclined to suppose that 

 such has been done by frugivorous animals. But for these plants also 

 we cannot do more than make guesses as regards the three cardinal 

 points of the problem, the fact, the time and the mode of import, 

 because there exists no unimpeachable evidence for direct introduction 

 of seeds or fruits by birds or other animals (which should not be 

 confounded with further dispersion over the island). Here, as every- 

 where in the Krakatao-problem, very many guesses have been made 

 but exceedingly little has been proven. It is unknown which plants 

 of the interior were imported before 1906, it is unknown when 

 they were imported, it is unknown in which way they were imported. 

 None of the Krakatao excursions has spread any other light on these 

 points than the often misleading twilight of guesses. 



In Chapter IV of his paper Ernst discusses the conditions of 

 life on Krakatao, especially the soil-conditions. On very good grounds 

 he argues that the soil of Krakatao was by no means so unfertile 

 as T r e u b meant. One very important source of plant-food is not 

 mentioned by Ernst, viz. the former vegetation of such higher parts 

 of the mountain as were soon laid bare or almost so by erosion. 

 This subject was already discussed on p. 73. 



In Chapter V of his paper Ernst excellently sets forth which 

 part water, wind and birds may have taken in carrying seeds, fruits 

 or spores to Krakatao. Below 1 give the essential parts of his 

 argument in an abridged form. 



The seeds of littoral plants are almost exclusively spread by sea-currents: one 

 finds them washed ashore everywhere. Experiments made with many of these seeds 

 have shown that they can remain floating for a shorter or longer time (1 120 days) 

 on sea-water or on a solution of NaCI without losing their germinative power. Even 

 such seeds as can float only one or a few days may quite well have been transport- 

 ed by the sea to KraUatao which is less than 45 km. distant from the surrounding 

 islands, because in the Sunda Straits, at least in the east-monsoon, sea-currents run, 

 which continue in the same direction for 18 hours with a minimal velocity of 3 km. an 

 hour. Seeds without floating power may be carried over in hollows or crevices of 

 tree-trunks or blocks of pumice. Rivers swollen by heavy showers carry not seldom 

 uprooted trees to the sea; part of the crown or of the root-system of these trees 

 often emerges from the water; not salt-resistent fruits or epiphytes can make the voyage 

 in this manner. The emerging part of the root-system often holds some soil in which 

 living plants or seeds may be present; mycelia of fungi may live in the wood. In 

 1906 two fungi which had formed fruit-bodies were found on tree-trunks washed ashore. 

 All these modes of transport may have contributed to make develop on the beaches 

 of Krakatao a rich vegetation not exclusively composed of typical littoral plants. The 

 lack of a mangrove-vegetation (consisting in the East Indian Archipelago of + 20 



