STUDIES IX THE VEGETATION OF THE PHILIPPINES, I. i 2o 



of the time they reql^ire in regions where the climatic conditions inhibit 

 growth entirely for a considerable part of the year. If bulk alone is 

 considered as a measure of success in forest growth, the virgin forests 

 of some parts of the temperate regions are surely more successful than 

 those of the tropics. This is especially true of the northwestern part of 

 the United States where exceedingly heavy stands of coniferous forests 

 occur. But if the annual increment is also used as an element of success 

 it is believed that some tropical regions are capable of producing more 

 bulk per year than temperate regions. Again, this is of economic 

 importance. While the land area of the north temperate zone is much 

 greater than that of the tropics and the absolute forest land (that is land 

 that is better fitted for forest growth than agriculture) is also much 

 greater, this inequality is in a measure offset by the possibility that each 

 acre of land in the tropics can probably produce from one and a half to 

 two crops of timber for one crop in temperate regions. A theoretical 

 discussion of the causes of the shorter lives of tropical trees is reserved 

 for another paper. 



I wish to express my thanks to E. D. Merrill, Botanist of the Bureau of 

 Science, for assistance in referring tree species to their scientific names, 

 and especially to H. M. Curran, Forester in the Bureau of Forestry, for 

 valuable suggestions in the preparation of this paper. 



