175 



an altitude of 2000 m. ! ) the south-east trade-wind blows throughout the year. Vagler 

 has proven for the Swiss Alps that there during storms a transport of seeds over a 

 distance of 20 km. is possible. In 1897 on Mount St. Gotthard a hail of salt-crystals fell, 

 the biggest of which had a weight of 4 g.; these crystals must have been transported 

 over a distance of at least 250 km., perhaps much more. The best proof, however, that 

 plant-germs may be carried through the air over large distances is furnished by Krakatao; 

 the seeds carried thither by the wind must originate from islands lying at distances 

 of 18 km. or more. 'I he first vegetation of the interior of Krakatao arose almost 

 exclusively from plant-germs introduced by the wind. These plants were algae, bacteria, 

 diatoms, Hepaticae, Musci, ferns and at least 6 of the 8 Phanerogams found by T r e u b 

 in the interior of the island. Ferns predominated with 1 1 species. According to P e n z i g, 

 till 1897 17 species, 32% of the total flora, were brought over by the wind. Ernst 

 believes that till 1906 28 species, 30% of all Phanerogams may have been carried to 

 Krakatao by the wind; for a number of these especially plants growing on or 

 near the beach he considers transport by water also as possible. Ernst considers 

 the arguments adduced by S c h i m p e r against transport of seeds by wind across 

 the sea as invalid. Light seeds, even those that possess no special adaptations for 

 floating through the air, can be spread over a large distance by winds having a 

 velocity of 30m. per second According to Ernst such winds are in the East Indian 

 Archipelago during storms by no means of rare occurrence. Hence light seeds and 

 fruits not possessing adaptions for floating through the air may have been carried 

 across the Sunda Straits, though such may more easily happen with seeds provided 

 with such adaptions. Spores and very light seeds, like those of orchids, may have been 

 transported by ordinary trade-winds; the heavier seeds // at least they were trans- 

 ported by the wind by heavy storms. 



From the above appears that we cannot exactly tell which part each of the 3 agents 

 of dispersal has taken in the revegetation of Krakatao. Probably the orchids were 

 brought by the wind, though another mode of transport is not to be considered impos- 

 sible; neither need the other anemochorous species have been imported by the wind. 

 The seeds and fruits of beach-plants may have come over either floating on the sea 

 or in crevices and hollows of driftwood and pumice; they may also have been carried 

 over by birds. Of the plants found till 1906 on Krakatao at least 39%, perhaps even 

 67 72%, were brought there by sea-currents. Nor can we make out with certainty 

 how many plants were imported by birds. Nearly all plants found on Krakatao have a 

 wide distribution over the Malayan Archipelago. The flora of the regions adjacent to 

 the Sunda Straits being very imperfectly known, we cannot trace the origin of such 

 species found on Krakatao as are not common in the Dutch Indies. Recapitulating, 

 Ernst arrives at the conclusion that by the wind were imported nearly all Cryptogams 

 and 16 30% of the Phanerogams, by sea-currents 39-72% of these latter, the rest 

 by birds. The import of so many Cryptogams should be ascribed to the fact that the 

 winds blowing in the Sunda Straits are strong enough to carry light spores over the 

 short distance that separates Krakatao from the surrounding islands. On the much 

 more remote Cocos-islands ferns are lacking -). Only 3 Cryptogams (a fungus, a moss 

 and a Lichen) have been found there. 



To this admirably lucid statement 1 need add but very little. 

 Doubtless plants of the interior may have been imported in various 

 ways, but of not a single species found till 1906 we know with 

 certainty that it has been imported, nor in which manner. That fruits 



l) Jung huh n says 2000 (old French) feet (of 0,3248395 m.) = 1950 m. 



-) I hat this lack of ferns is indeed to be ascribed to the long distance separating 

 the Cocos-islands from |ava and not to climatic or edaphic influences, is no more 

 proven than the precisely opposite statement of Treub that the long distance separ- 

 ating |uan Fernandez and Ascension from the nearest continent is the cause of the 

 abundance of ferns in these islands. See p. 76 seq. 



