:HAr. I] THE FORMATIONS r«^ 



iv. TKANSJTIO.Y FROM EDAPHIC INTO CLIMATIC FORMATIONS. 



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

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

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

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

 either of woodland nor of grassland, and which assume nearly the same 

 ppearance even in dissimilar climates, and owe their individuality chiefly 

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

 ransitional formations into the definite ones of woodland and grassland 

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

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

 f their sequence only by comparing their condition at difterent ages, 

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

 cry slight attention has hitherto been paid to it. 



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

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

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

 shes. 



As has been already stated ', the vegetation of Krakatoa at the time of 

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

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

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

 le earliest Diacroscopic vegetation. They are preceded by a microscopic 

 :getation of Cyanophyccac, zvhich cover in a thin film ilie wJiolc surface 

 '^ ash and puuiicc, and prepare the soil for the development of ferns. 



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

 untur in West Java, which, by the eruption of 1S43, had been covered 

 Dwn to its base with large hot heaps of detritus-. Naturally I found 

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

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

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

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



irly numerous both in species and individuals, without however forming 

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

 y' plants that grew as epiphytes in the neighbouring woods, namely 



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

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

 imp air, and rich illumination, and which could thus, undisturbed b}' 

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



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



' Page So. - See Junghuhn, op. cit., \'ol. II. p. 392 



