24 



in Luzon, all extinct volcanoes, each one plainly visible from 

 the other and each supporting a characteristic type of primeval 

 forest each presents a fairly large number of species, at approxi- 

 mately similar altitudes, that have not been found on either 

 of the other two. 



In regard to the high altitude flora of the Philippines most 

 of our higher mountains present a certain number of species 

 in common. The tendency is for each mountain, at least those 

 peaks that are widely separated, and those located on different 

 islands, to present a marked local endemism. This will doubtless 

 prove to be true for the whole Malayan region, or at least in 

 many parts of this vast area. 



Again in Verde Island passage between Luzon and Mindoro, 

 which is only seven and one-half miles wide in its narrowest 

 part, in March to June the Batangas shore is always brown and 

 barren looking while the Mindoro coast supports a most luxu- 

 riant type of vegetation, green and fresh at all seasons. 

 Epiphytes such as Asplenium nidus occur on the Mindoro coast 

 in mangrove trees overhanging tidal streams, which occur in the 

 opposite parts of Batangas only at and above an altitude of 

 about 2,000 feet; in this case the explanation of this diversity 

 in vegetation in areas separated by only a narrow arm of the sea 

 is that Batangas is subject to a prolonged dry season while on 

 the opposite coast of Mindoro rains are more or less frequent 

 in all months on account of the high mountains of Mindoro 

 situated not far from the coast. The disposition of mountain 

 masses has a marked effect on the seasonal distribution of the 

 rainfall, and thus an equally marked effect on the nature of the 

 vegetation at low altitudes in the vicinity of such mountains. 

 In Malaya there is doubtless a large number of local and not 

 widely separated areas that present contrasts in their vegeta- 

 tion as striking as the one mentioned above. 



Again the geologic formation in relation to the vegetation 

 must be considered, the flora of areas of volcanic origin being 

 rather strongly differentiated from that of limestone regions; 

 while such regions present many species in common, others are 

 characteristic of the limestone areas and are scarcely to be 

 found on other geologic formations. The richness of a local 

 flora is naturally always greater in those regions where there 

 is a considerable range in altitude, and the forested areas are 

 usually much richer in species than are the open grasslands 

 and settled areas. 



The tropical forest characteristic of most parts of Malaya 

 is exceedingly complex. In the Philippines an examination of 

 the stand on definite areas may show more than one hundred 

 different kinds of trees on as small an area as one-fourth of a 



