3 o6 



ZONES AND REGIONS 



[Pt. Ill, Sect. I 



thickness as occur in dry tropical districts. They are, on the contrary, more 

 frequently quite smooth, or marked by shallow longitudinal and transverse 



fissures. Indeed, the forma- 

 tion of cork is often so 

 poor that moderately thick 

 stems are green owing to the 

 chlorophyll of the cortical 

 layers being visible through 

 it. It is possible that the phe- 

 nomenon of cauliflory, which 

 will be described further on, 

 is connected with the feeble 

 development of bark. 



Rarely in the forest has 

 one an opportunity of gain- 

 ing an insight into the pre- 

 cise arrangement of the 

 branches, for to achieve this 

 the tree must be felled. 

 In this respect again the 

 Buitenzorg garden gives 

 ample opportunity for study, 

 although it should always 

 be remembered that, besides 

 trees of the rain-forest, it 

 also contains trees of de- 

 ciduous forest, of littoral 

 forest, and even of savannah. 

 The very striking forms of 

 umbrella-like trees are quite 

 exceptional in the evergreen 

 virgin forest — and even then 

 they are usually giants of 

 the forest, whose crowns 

 tower above the general 

 leaf-canopy — whilst the still 

 more striking forms of the 

 trees with their branches in 

 tiers seem to be entirely 

 absent from them. Such 

 forms of trees are far more characteristic of well-lighted, deciduous, more 

 or less xerophilous forest, of savannah, and of the highest forest region 

 in the mountains, in short, of a dry climate. The crowns of the trees 



Fig. 144. Schizolobium excelsum. 

 by Treub. 



After a photograph 



