24 SYLVICULTURE IN THE TROPICS n. i 



open forest with scattered large trees such as Khaya 

 spp., Parkia Jilicoidea, Daniellia thurifera, Berlinia 

 acuminata, Afzelia africana, Tamarindus indica, 

 Eryihrophlaeum guineense, with a variety of species 

 belonging to the natural order of the Combretaceae 

 and numerous shrubs. It is in this zone that a large 

 number of rubber-yielding creepers will be found festoon- 

 ing the trees, such as Landolphia spp. and Clitandra 

 spp., also the rubber-yielding tree Funtumia elastica. 



According to Schimper * high forest does not occur 

 except where the rainfall is 1800 millimetres and over. 

 By this, I presume, he means forest composed largely 

 of tall trees standing so close together that their crowns 

 meet, or, in forest parlance, that they form " leaf- 

 canopy." No doubt, although on the central African 

 plateau the slopes and summits of the undulations are 

 steppe-like or covered with an open growth of trees, yet 

 the bottoms of the valleys are frequently filled with 

 dense growths of trees, such as the " gallery-forests" of 

 Schweinfurth, 2 but they derive a large proportion of 

 their moisture from the watercourses whose banks they 

 line. 



In tropical America, according to Schimper, 3 this 

 zone is also represented by an open kind of forest, 

 known, according to the locality, as " campos," " llanos," 

 ; ' caatinga," or " savannah," and composed largely of 

 deciduous trees including, towards the north, a number 

 of Cactaceae and Euphorbiaceae, while towards the 

 south the trees are leafless only a very short time. 

 Heavy forest is mostly confined to bottoms of valleys. 

 This zone is important economically on account of 

 the rubber- yielding trees which grow within it, 

 the " Ceara - rubber " tree or "Manicoba" (Manihot 

 Glaziovii, M. dichotoma, M. piyaultc/tsis, etc.) and the 

 'Para-rubber" tree (Hevea brazilie?isis) being the 

 more prominent, the former in the open savannah 

 forests of Northern Brazil, and the latter in the basin 

 of the Amazon. 



Plant Geography. - Heart of Africa. * Plant Geography. 



