IX, A, 5 Brown and Mathews : Dipterocarp Forests 467 



any given time. When we come to consider the growth of 

 plants in a forest we find conditions quite different, owing to 

 the density of the vegetation, and it is doubtful if any of the 

 plants, except possibly some of the largest trees, are under 

 exceptionally favorable conditions at any time. It should not 

 surprise us, therefore, that forest trees show relatively slow 

 rates of growth. 



Great difficulty is encountered in any attempt to estimate 

 the age of forest trees in the Philippines. In no case has it 

 been demonstrated that annual growth rings are present. An 

 effort has been made in this paper to determine the probable age 

 and rates of growth of some of the most important commercial 

 species by using the rates of growth on large numbers of indi- 

 vidual trees for a period of one or a few years. It is evident 

 that the results obtained cannot be absolutely accurate, but owing 

 to the large number of different size classes employed it is be- 

 lieved that the results will give a fair indication of the rates of 

 growth of trees in a virgin forest. 



The growth data presented in this paper are the results of 

 two series of measurements. One series, including all the 

 growth data from the forest of northern Laguna and Mount 

 Maquiling, consists of very careful measurements made at in- 

 tervals of from one to three months for a period of one year. 

 The trees were measured at breast height in every instance, 

 except where buttresses made measurement at a higher point 

 unavoidable. The results are presented in the form of diameter 

 growth, but the measurements were taken with a steel tape 

 and were, of course, originally girth measurements. In order 

 to be certain that the measurements were taken at the same 

 point each time, shingle nails were driven into the trees, for a 

 short distance, just below the tape, at the time of the first 

 measurement. In only a very few instances did the nails cause 

 the production of swellings, and such cases were discarded. 



The growth data for trees in Bataan Province are based on 

 2 measurements taken at an interval of either eight or nine 

 years. The trees are located in 4 different places at varying 

 elevations in the Lamao forest reserve. They were selected and 

 measured by officers of the Bureau of Forestry in 1905 or 1906. 

 All of the measurements, with the exception of those on type 

 area C at an elevation of 700 meters, were made in 1906 by 

 Forester W. M. Maule, with a steel tape 1.37 meters (4.5 feet) 

 above the ground and at a point 1 meter above a notch cut in 

 the trunk of the tree. Those on type area C were first measured 

 in 1905 with calipers, 2 measurements being taken, the first 



