CHAP. LXXXI SAVANNAH-FOREST 301 



present condition of our knowledge does not permit of our giving any 

 final answer to the query. But it may be regarded as certain that the 

 phenomenon is intimately associated with edaphic and climatic con- 

 ditions. Both in steppe and in savannah we have seen that very xero- 

 phytic bushland is the most accommodating, and that, as the external 

 conditions are gradually ameliorated, there succeed, in order, grass- 

 formations, semi-mesophytic bushland (sibljak, and savannah-forest), and 

 finally mesophytic forest. And side by side with secular changes in soil 

 and climate corresponding modifications have affected the vegetation. 

 In certain cases other factors, for example fires, have co-operated in 

 producing the result. The Brazilian upland presumably was originally 

 clothed with forest, but as the land increased in extent the central and 

 oldest parts gradually acquired a continental and drier climate, and forest 

 was changed into the campos. 1 In this case the peculiar forms assumed 

 by the trees and many other plants are not caused by climate alone, 

 but also by fires on the campos. The savannah in Java and Sumatra has 

 arisen, according to Junghuhn, 2 through destruction of forests. 3 The 

 llanos are clothed with a relatively recent vegetation, which has immi- 

 grated from the mountains of Guiana and Venezuela. 4 Between the 

 antiquity of a vegetation and the number of its species a certain pro- 

 portion exists. The llanos, pampas, and prairies are, in accordance with 

 the foregoing remarks, obviously more recent, and at the same time much 

 poorer in species, than are the ancient highlands of Brazil and Guiana. 

 Moreover, the poverty in species of the forests of northern Europe is 

 certainly to be ascribed to the relative recency of this vegetation since 

 the Glacial Epoch. 5 



APPENDIX 



Evergreen Tropical Bushland. 



In some tropical spots, where the rainfall is small but there is no 

 marked dry season, xerophytic evergreen bushland and bush-forest come 

 into existence. Such is the case in the Madras Province, in southern Java, 6 

 and in the West Indies. 



Dry tropical bushland in the West Indies is oecologically closely related 

 to the Mediterranean maqui, 7 though differing widely from this as 

 regards flora. The Danish and some other isles of the Antilles that have 

 but a slight rainfall are largely clothed with a grey, desolate, useless, and 

 scorching bushland, between whose thorny, tangled shrubs and low trees 

 one cannot penetrate without the aid of an axe. A grey felt of hairs coats 

 many species, including those of Croton, which in places dominate to such 

 an extent as to form extensive, almost pure associations (crotoneta), for 

 instance, in the eastern parts of St. Croix 8 ; a similar coating clothes the 

 aromatic verbenaceous Lantana, species of Cordia, and Melochia tomen- 

 tosa. Other plants, on the contrary, display fresh-green glossy foliage ; 

 one usually sees these species standing out from the grey bushy vegetation 

 as isolated dark-green patches, which provide a striking contrast that is 



1 P. V. Lund, 1835 ; Wanning, 1892, 1899. * Junghuhn, 1852-4. 



3 Concerning the patanas of Ceylon, see p. 298. * Ernst, 1886, p. 313. 



6 Warming, 1899. " Junghuhn, loc. cit. ; Schimper, 1893. 



' See Chapter LXXXIV. * Eggers, 1876. 



