Chap. V] TROPICAL DISTRICTS WITH DRY SEASONS 351 



an erect mode of growth 1 . Lianes also disappear in the low shrub- 

 formations of Northern Brazil. In savannah-forest and thorn-forest, into 

 which savannah and shrublands pass when the humidity increases, they 

 are sometimes found in small numbers and poorly developed. 



Epiphytes belonging to the Phanerogamia and Pteridophyta are very 

 scantily represented on the trees in well-lighted xerophilous savannah- 

 woodland, or are entirely absent. They become more abundant as soon as 

 the trees grow closer together, and many a savannah-forest is by no means 

 poorly decked with Bromeliaceae, Orchidaceae, Cactaceae, and ferns. Even 

 epiphytic species of Ficus, and perhaps of Clusia, occur in savannah, where 

 they appear to be confined to palms, the persistent petiole-bases of which 

 serve as receptacles for the young plants (Fig. 200). In all the epiphytes 

 of such dry formations the xerophilous character is most pronounced ; 

 all protective measures against the loss of water, and all devices for the 

 collection and retention of rain-water, with which we are already ac- 

 quainted, are specially well developed in them. Yet, with the exception 

 of the figs, they are only small forms. 



Eminently characteristic as is this epiphytic flora of the xerophilous 

 tropical district, and perfectly as it is adapted to the climatic conditions 

 prevailing in the district, yet it is composed exclusively of species from the 

 rain-forest. The highest branches of the virgin-forest trees, those in fact 

 that receive sunlight almost without hindrance, are the homes of the 

 savannah epiphytes. It is from the virgin forest that they have colonized 

 the dry tracts of country 2 . 



2. WOODLAND FORMATIONS IN PERIODICALLY DRY 

 TROPICAL DISTRICTS. 



i. GENERAL REMARKS. 



The change in the vegetation on passing from a constantly humid tropical 

 district into one with abundant rainfall but periodically dry, appears only 

 slight during the wet season, but is manifested in the dry season, particularly 

 by the great number of defoliated trees. 



Trees that are at times bare of foliage are very scantily represented in 

 the rain-forest and are usually not noticed at all, the less so that their 

 defoliation and foliation have frequently no connexion with the seasons of 

 the year. If however one proceeds during the dry season, for instance, 

 from the constantly humid West Java to East Java, where there is very 

 little rain during the east monsoon, the foliage becomes very thin, as it has 

 been completely shed by many trees and partially so by others. In 

 addition to this, slight influences exerted by the soil suffice to call into 

 being the teak-forest, which is almost completely leafless in the dry 



1 Schenck, I, p. 60. 2 See p. 199. 



