22 The Philippine Journal of Science 1923 



far as known being confined to New Guinea. He states that 

 the family plays an unimportant role in Papua and considers 

 that there is no reason to believe that future investigations will 

 greatly increase the number at present known. 



He makes the significant statement that, while the species 

 hitherto established are in part too imperfectly known to allow 

 of positive systematization, those that are sufficiently well known 

 stand in close relationship with species of Celebes and the Philip- 

 pines; there are no apparent indications of independent form 

 structure for the New Guinea species. He concludes that the 

 Dipterocarpaceae represent a younger element in the New Gui- 

 nea flora, an element which has been derived from the northwest 

 by way of Celebes and the Philippines. This conclusion was 

 reached by Doctor Diels solely on the indicated botanical rela- 

 tionships of the New Guinea species, and is absolutely in accord 

 with the general conclusions I have drawn regarding the origin 

 of the Philippine flora in relation to the geographic distribution 

 of the Dipterocarpaceae. This apparent derivation of the Pa- 

 puan Dipterocarpaceae from the northwest, that is, Celebes 

 and the Philippines, may perhaps be interpreted as supporting 

 the idea that in previous geologic epochs a drier climate charac- 

 terized the lesser Sunda Islands, and perhaps southern Java, 

 which would, of course, inhibit the eastern extension of hygro- 

 phytes over this southern route into Celebes. The only possible 

 route under these conditions between western Malaysia and 

 New Guinea would then be through Borneo, the Philippines, 

 Celebes, and the Moluccas. 



There are, of course, other than strictly geologic factors 

 to be taken into consideration in discussing the differences be- 

 tween eastern and western Malaysia. As Mr. I. H. Burkill has 

 recently indicated to me, there is the possibility that in past 

 geologic epochs the climate of southern Java and of the lesser 

 Sunda Islands may have been drier than it is to-day; even to-day 

 the climate of Timor and of the lesser Sunda Islands generally 

 is drier than that of other parts of Malaysia. This would have 

 the effect of inhibiting the extension of the dipterocarps and of 

 other plants, as well as animals, that are adapted to humid 

 conditions eastward through the southern part of Malaysia and 

 this may in part explain the absence of dipterocarps in Timor 

 and the lesser Sunda Islands. We must, however, not overlook 

 the tact that there has also been much destruction of life on some 

 of the smaller islands in this particular region by volcanic erup- 

 tions. The swift currents through such narrows as the Lombok 



