442 The Philijypine Journal of Science 1923 



it seems highly probable that many of the species may be distributed 

 through their seeds being present in mud adhering to the feet or feathers 

 of migratory birds, as in numerous cases very minute seeds are produced 

 in great abundance, corresponding in general to the large series of rice- 

 paddy weeds so predominant in the open low-country vegetation of the 

 Philippines, and whose distribution can scarcely be explained on the basis 

 of any other hypothesis than that just mentioned. 



It is to be noted that the northern types are for the most part 

 confined to the Benguet-Bontoc region in the Philippines. Many are 

 essentially Himalayan, but others are confined to China and Luzon, For- 

 mosa and Luzon, and a few to Japan and Luzon. Practically all of the 

 Himalayan types found in Luzon also occur in Formosa, indicating that 

 they attained their present distribution at probably the same geologic 

 time. It would seem that this might have been in the Oligocene or 

 Lower Miocene age when Formosa and Luzon were connected with the 

 Asiatic continent. These types may have at one time extended farther 

 south, but if so, they have been exterminated by changes in climatic 

 conditions. Very many of the Formosan-Luzon-Himalayan types are un- 

 known from Sumatra, Java, and Borneo, and could scarcely have reached 

 Luzon and Formosa through those islands. Summarizing, it would seem that 

 from the time these Himalayan types reached the Philippines there has 

 been continued high elevation in some part of the Benguet-Bontoc region, 

 which has allowed them to persist. Most or all of them cannot grow 

 under present climatic conditions at altitudes below 1,200 meters, while 

 very many of them cannot grow below altitudes, of 2,000 meters. 



As far as Malaysia as a whole is concerned there were apparently 

 two independent series of migration of Asiatic types, one through the 

 Malay Peninsula to Sumatra, Java, Borneo, and the Philippines, and an 

 earlier one through Formosa and Luzon to the Philippines, a few of 

 which extended southward to Celebes. 



Mr. Merrill's illuminating description clearly indicates that, 

 at least since the beginning of the Miocene, mountains attaining 

 elevations of 900 to 1,500 meters existed in Luzon. After the 

 uplift of Baguio Plateau in middle or late Pleistocene time, the 

 temperate flora from the greater heights of northern or southern 

 Luzon invaded the newly formed Baguio Plateau, approved of 

 its climate, and has continued to flourish there. 



ACCELERATED TROPICAL PENEPLANATION 



As was outlined in the introduction, the development of Baguio 

 Plateau was rapid and the northern extension of this surface 

 was great, according to Doctor Smith who correlates Mount 

 Data Plateau with it. Now, the reader must remember that 

 this surface cuts transversely the Baguio formation of probably 

 late Pliocene or early Pleistocene age. This early old-age sur- 

 face, or peneplain, was developed in the Pliocene, uplifted 

 in the Pleistocene, and has over much of its former extent been 

 chopped up into knife-edged mountain ridges 1,200 to 2,100 



