250 E. D. Merrill 



islands of the Philippines, Celebes, the Moluccas, and New 

 Guinea, there are numerous mountains from 5000 to 8000 feet 

 high, with peaks at least 10,000 feet high in Sumatra, Java, 

 Celebes, Luzon, and Mindanao. The maximum elevations are 

 13,700 feet in Borneo and about 16,000 feet in New Guinea. 

 These high mountains form "islands" within the tropics where, 

 once established, species adapted to temperate and subtemperate 

 conditions have persisted. Certain parts of the archipelago have 

 prolonged alternating wet and dry seasons in each year, and 

 others have a rather uniform distribution of rainfall in all 

 months of the year. In the great islands, there are no regions that 

 approach arid or even semiarid conditions, and there is perhaps 

 only one part of the entire region where the restricted annual 

 rainfall appreciably affects the vegetation. This part comprises 

 some of the Lesser Sunda Islands. The rainfall — its amount and 

 its seasonal distribution — is the most important single factor, 

 aside from altitude, which affects the distribution of vegetative 

 types in all Malaysia. At low altitudes, the remarkably uniform 

 temperature has had litde limiting influence on the distribution 

 of plants. The prevailing winds, which affect vast areas for sev- 

 eral months each year, are of minor importance to vegetative 

 types except as they affect the seasonal distribution of rainfall. 

 There are no striking differences in soil types except in limited 

 areas. Therefore, neither precipitation, humidity, temperature, 

 nor soil conditions can cause the vegetation of any major part 

 of the Archipelago to be strikingly different from that of any 

 other major part at a similar altitude. 



Yet there are remarkable differences in dominant families, 

 genera, and species between the known flora of any two great 

 islands, or contiguous groups of islands, particularly between 

 eastern and western Malaysia. It is true that most of the families 



