218 OUTLINE OF PLANT GEOGRAPHY 



dated with these trees were a number of leguminous shrubs 

 wit h yellow or purple flowers, and climbing over trees and shrubs 

 were various lianas, including several showy Ipomoeas, and a 

 species of Gnetum, with salmon-pink berries. The latter repre- 

 sents a small family of gymnosperms, the Gnetaceae. 



Forest Trees 



As already indicated the most important trees are the Dip- 

 terocarps, but besides these is an extraordinary variety of other 

 large trees. The most important families are the Rubiaceae, 

 Leguminosae, Ebenaceae, Sapotaceae, Artocarpaceae, Tiliaceae, 

 Bombacaceae, Dilleniaceae and Euphorbiaceae. The Rubiaceae 

 take first place in the Bornean flora, the Orchidaceae second. 



Sumatra 



Separated by the Straits of Malacca from the Malay Pen- 

 insula, is the great island of Sumatra, about 1,100 miles long, 

 by 250 in breadth, and almost exactly bisected by the equator. 



The topography of the island is comparatively simple. Parallel 

 with the west coast, and descending to it abruptly, is a mountain 

 range, in places exceeding 10,000 feet elevation. Between this 

 range and the east coast is an extensive low alluvial plain. 



The mountain ranges are composed largely of Palaeozoic 

 rocks, granites, schists, quartzite, slate and limestone, but there 

 are later deposits also, and some extensive volcanic formations 

 including a number of active volcanoes, some of them approach- 

 ing 10,000 feet altitude. 



The climate is of the true equatorial type, with very little 

 variation of temperature, and for the most part abundant rain- 

 fall. The west coast has a heavier rainfall than the east, approach- 

 ing 200. inches annually at some points. The driest districts 

 are in the northeast on the lee-side of the mountains. 



While the vegetation has been pretty well investigated in 

 some parts of Sumatra, much of the country is still very little 

 known. The fertile eastern plains have been cleared of the 

 heavy forest over considerable areas, and the usual tropical 

 crops are grown. Of late years Sumatra has become a very 

 important source of rubber, of which extensive plantations 

 now exist. Tobacco culture is also a very important industry. 



