THE PALAEOTROPK ■ 



east of this line was predominantly Australian. A study of the 

 vegetation shows plainly that the floras of these eastern islands 

 also show a distinctly Australian influence, although much 1< 

 marked than the animal life. 



The subject has been investigated by later investigators, and 

 a recent paper by Dr. E. D. Merrill l gives an admirable summary 

 of the subject. Wallace's line is extended northward to the w< 

 of the Philippines, Palawan being the only large island lying to 

 the west. This line is supposed to mark the edge of the Asiatic 

 continental shelf. A second line, Weber's line, running close to 

 New Guinea and Australia, marks the edge of a second continental 

 shelf upon which are situated Australia and New Guinea. The 

 two continental masses are separated by an archipelago, of which 

 Celebes is the largest member. 



There is a marked difference between the eastern and western 

 Malaysian floras, although they have a very large number of 

 forms in common. There are 356 Malaysian genera confined to 

 western Malaysia, and 225 which do not occur west of Wallace's 



line. 



It is assumed that the two continental regions have been rela- 

 tively stable, but the region between shows evidences of frequent 

 elevations and depressions, with probable temporary connections 

 with one or the other of the continental areas, thus permitting an 

 occasional interchange of plants. This accounts for the presence 

 of such distinctly Australian types as Eucalyptus, Casuarina, and 

 Melaleuca, in the western part of Malaysia. 



The contrast between the floras of western and eastern Malaysia 

 may be illustrated by the distribution of the essentially western 

 Malaysian family, the Dipterocarpaceae. In the Sunda Islands, 

 there are eleven genera and 144 species, while in the whole of the 

 region east of Wallace's line, including the great islands of Celebes 

 and New Guinea, there are but four genera and fourteen species, 

 and possibly this number may be reduced as some of the recorded 

 species are doubtful. 



The Molucca or Spice Islands, lying between Celebes and New 

 Guinea, were formerly of great importance commercially, as the 

 main source for such spices as pepper, cloves, nutmegs. The 



i "Distribution of the Dipterocarpaceae," PhUippii rnal of & VcL 



XXIII, No. 1., July, 1923. 



