29 



means proof that these species have established themselves on the 

 island after 1908; all of them may have grown there long before, 

 The remarks ') ,,that in 1919 in the lower ravines a great many more 

 plants occurred than formerly", that ,,most of these plants were 

 not yet present on the island at the time of the first expeditions" 

 and ,,that the number of forest-plants has been greatly added to", 

 lack a firm scientific base. It is not certain, not even probable, that 

 in 1919 the same ravines were examined as in 1908. Of course I will 

 not at all deny the possibility of new plants having immigrated after 

 1908, but this is a mare supposition and the Krakatao- problem did 

 not derive its importance from the occasion to make more or /ess 

 plausible guesses but from the supposed possibility to determine with 

 certainty the origin and development of the new flora. 



I fully acknowledge that the situation in 1906 and 1908, resp. 23 

 and 25 years after the eruption, gives only an indication but no 

 proof for the correctness of my views. But the total destruction of 

 the old flora is just as little proven and, moreover, not at all probable. 

 It is much to be regretted that T r e u b, considering the total des- 

 truction of the old flora as a dogma, has not seen the necessity of 

 sending a well-equipped expedition to Krakatao, as soon as possible 

 after the eruption. Such an expedition ought to have been repeated 

 several times and to have been charged with instituting throughout 

 the island and especially in the higher ravines minute investigations 

 after rests of the old flora, which might have survived the catastrophe. 

 This has been neglected, and therefore Treub's argumentation, 

 based on theoretical considerations and very incomplete investiga- 

 tions, moreover contradicted by probability, lacks all conclusive force. 



Yet another part of the present island Krakatao has not been 

 covered with a permanent thick layer of coarse pumice-materials. 

 I have here in view the basaltic slope, which begins at Zwarte Hoek 

 and runs up rather high against the mountain. This locality was des- 

 cribed by P e n z i g -) as follows : ,,Die z. Th. aus hartem Lavafels 

 ,,bestehenden, z. Th. von Bimsstein und Lavatrummern bedeckten 

 ,,Abhange sind sehr steil. Das Haupthinderniss" (to the ascent) ,,bilden 

 ,,unzahlige, oft auszerordentlich tiefe Spalten und Klu'fte. Diese Klu'fte, 

 ,,wahrscheinlich durch die Contraction der erkaltenden Lava gebildet, 

 ,,gahnen an ihrem obern Rande oft viele Meter weit, wahrend die steil 

 ,,abstiirzenden Wande sich erst in unabsehbar dunkler Tiefe vereinigen". 



!) Docters van Leeuwen in Handelingen Eerste Ned. Ind. Natuurvvet. Congres 

 <1920) p. 47.-Ann. du lard. Bot. XXXI (1921), p. 58, p 117. 



2) Ann. lard. Bot. Buitenzorg, 2me Serie, Vol. Ill (1902), p. 96. 



