37 



of the mobility of the loose materials and which bore as late as 

 1908 only a very scanty vegetation. The second region consists of 

 the almost bare, easily accessible rocks of Zwarte Hoek and the 

 steep slopes above it, the latter being ploughed by deep ravines 

 and partly covered with ashes and pumice. Treub himself did not 

 describe the locality investigated but Penzig 11 years afterwards 

 gave the description quoted on pp. 29, 30. The rocky unweathered 

 parts of the locality must have been (Cf. p. 30) very sterile; plants 

 could only live in crevices and hollows and this was in the east- 

 monsoon only possible because on Krakatao this monsoon, as a 

 rule, is not strong, so that sheltered localities do not dry up much 

 (Cf. p. 26, footnote I). 



From his finds Treub drew a number of conclusions which 

 in consequence of the very defective knowledge extant in his time 

 of the condition of life and the area of Indian plants, appeared quite 

 correct and were universally accepted. But now they can be no more 

 admitted to their full extent. Therefore I shall first discuss the plants 

 found bij Treub, secondly the conclusions drawn by him, and in 

 the third place I shall consider these conclusions in the light of our 

 present knowledge. 



Of the plants found by Treub unfortunately only the ferns, 

 determined by B u r c k, are preserved in the Buitenzorg Herbarium. 

 As to the higher plants it seems that only their names were noted 

 down by Treub but that no specimens were collected or at least 

 preserved, so that, for these, it is impossible to control the determi- 

 nation, a precaution which cannot be considered unnecessary for lists 

 of plants dating from that time, as will appear from my discussion 

 of the ferns. The fern-material has been preserved in a good condit- 

 ion but in consequence of the quite inadequate labelling it is of 

 little or no value for oecological purposes: the labels only bear the 

 note Krakatao or Zwarte Hoek; data about habitat, altitude above 

 sea-level and frequency are entirely lacking. Neither in T r e u b's 

 publication information on these points is found. Only by examining 

 the conditions of life and the area of distribution in the Dutch Indies 

 of the species found by him, one can get some rough idea of the 

 composition of the fern-vegetation in the locality investigated in 

 1886; a detailed account is impossible. As to the higher plants of 

 which the identity is partly not established the conditions are yet 

 worse. Barring the general communication that they were scattered 

 and few in number we know about those higher plants next to nothing 



