30 The Philippine Journal of Science 1923 



Celebes and Borneo across the Macassar Strait since the early 

 Tertiary, but indirect connections have existed through Borneo 

 and Celebes via the Sulu Archipelago, Mindanao, and the Sangi 

 Islands, and probably also between eastern Java, Bali, Lombok, 

 and other smaller islands and southwestern Celebes. The south- 

 ward extension of Wallace's Line through the Lombok Passage, 

 as well as its northern extension through the Sibutu Passage, 

 the Sulu Sea, and the Mindoro Strait has not been as strongly 

 marked nor as persistent as the Macassar Strait, and hence has 

 not been as efficient a barrier to the passage of animals and 

 plants as has the narrow strait between Celebes and Borneo. 



3. Weber's Line, so named by Pelseneer, is apparently the 

 approximate eastern boundary of the unstable area, separating 

 the insular region from the continental and stable areas now 

 delimited by the continental shelf surrounding and uniting New 

 Guinea and Australia. Geologically, this is ranked by Molen- 

 graaff as the most important dividing line in Malaysia. Bio- 

 logically, it apparently ranks with Wallace's Line as an important 

 dividing line between the Moluccan-Timor regions and Australia, 

 quite as Wallace's Line separates western from eastern Ma- 

 laysia. This paper then is essentially a re-interpretation of 

 Wallace's Line, botanically tested, as well as a test of Weber's 

 Line. 



4. The Dipterocarpaceae present eleven genera and one 

 hundred thirty-five species in the Eastern Peninsula, eleven 

 genera and one hundred forty-four species in the Sunda Islands, 

 nine genera and fifty species in the Philippines, and only four 

 genera and fourteen species in the entire group from Celebes 

 to New Guinea southward to Lombok and Timor. A study of 

 the Malaysian distribution of all the Malaysian genera of flower- 

 ing plants shows about three hundred fifty-six genera in western 

 Malaysia that are unrecorded from eastern Malaysia, of which 

 two hundred eighteen, or 61 per cent, reach the Philippines; 

 and about two hundred twenty-five genera in eastern Malaysia 

 that do not reach western Malaysia, of which fifty-six, or about 

 25 per cent, reach the Philippines. The Philippine flora thus . 

 presents strong relationships with the floras of both Papua 

 and Sunda Land. The evidence from the geographic dis- 

 tribution of the Dipterocarpaceae conforms entirely with the 

 general generic distribution of all groups of flowering plants in 

 the whole Malaysian region, indicating previously existing and 

 rather long continued land connection between the Philippines 

 and Borneo via the Sulu Archipelago to the south and the 



