Chap. I] THE FORMATIONS 185 



iv. TRANSITION FROM EDAPHIC INTO CLIMATIC FORMATIONS. 



Between the bare hard rock and the finely grained soil that finally 

 results from it, for the possession of which there is a struggle between 

 woodland and grassland, there is, according to what has been said 

 above, a series of open transitional formations, which possess the character 

 neither of woodland nor of grassland, and which assume nearly the same 

 appearance even in dissimilar climates, and owe their individuality chiefly 

 to the mechanical texture of the soil. The transformation of these 

 transitional formations into the definite ones of woodland and grassland 

 is continually proceeding under our eyes, but so slowly that we can 

 observe only a part of the process directly, and can form an estimate 

 of their sequence only by comparing their condition at different ages. 

 In spite of the highly interesting nature of the development of formations 

 very slight attention has hitherto been paid to it. 



An excellent piece of work in this respect is Treub's description of 

 the vegetation at Krakatoa three years after the well-known eruption, 

 which covered the whole island with a hot deposit of pumice and 

 ashes. 



As has been already stated 1 i the vegetation of Krakatoa at the time of 

 Treub's visit consisted chiefly of ferns (eleven species), whilst phanerogams 

 appeared only isolated and almost exclusively on the sea-shore. Ferns 

 thus form the earliest vegetation on volcanic islands — or rather only 

 the earliest macroscopic vegetation. They are preceded by a microscopic 

 vegetation of Cyauophyccac, which cover in a thin film t/ie whole surface 

 of ash and pumice, and prepare the soil for the development of ferns. 



By the advice of my honoured friend Treub, I visited the volcano Gunong 

 Guntur in West Java, which, by the eruption of 1843, had been covered 

 down to its base with large hot heaps of detritus 2 . Naturally I found 

 the vegetation there in a far more developed stage than Treub did in 

 Krakatoa, yet it was still quite open and on the whole very poor. There 

 were absolutely no trees, but shrubby and herbaceous plants of very 

 various species were present (Fig. 100). As in Krakatoa, ferns were 

 fairly numerous both in species and individuals, without however forming 

 the main mass of the vegetation. The most essential part was played 

 by plants that grew as epiphytes in the neighbouring woods, namely 

 many orchids, as well as several ferns and the shrubby Rhododendron 

 javanicum, which found suitable conditions here, such as a hard substratum, 

 damp air, and rich illumination, and which could thus, undisturbed by 

 competitors, take possession of the soil. It was also interesting to find 

 numerous specimens of a Nepenthes, the pitchers of which held such 



1 Page 80. 2 See Junghuhn, op. cit., Vol. II, p. 392. 



