THE PHILIPPINE 



Journal of Science 



A. Chemical and Geological Sciences 

 AND THE Industries 



"V^^^yi^t^ 



Vol. IX NOVEMBER, 1914 No. 6 



PHILIPPINE DIPTEROCARP FORESTS 



By William H. Brown and Donald M. Mathews 



{From the Botanical Section of the Biological Laboratory of the 



Bureau of Science and from the Division of Investigation 



of the Bureau of Forestry, Manila, P. I.) 



(Concluded.) 



SEASONAL DIAMETER GROWTH 



Parashorea plicata was the only dipterocarp which it was 

 practical to measure frequently enough to obtain seasonal rec- 

 ords of growth, and for this reason such records are confined 

 to it. Measurements of girth were made at intervals of ap- 

 proximately two months on the same trees that were used in 

 obtaining yearly records. For the sake of comparison the girth 

 records were reduced to terms of diameter growth for thirty-day 

 periods. The results are recorded in Table XXXIX. The aver- 

 age rates of growth compiled from this table are plotted for all 

 diameters in fig. 12. The most striking thing about the curves 

 is that they show two periods of rapid and two of slow growth. 

 The first period of slower growth is most apparent at the height 

 of the dry season in April. After this, the rate of growth 

 increases steadily until June and July, just after the beginning 

 of the rainy season. From the end of July to the first of 

 October there is another decided minimum, and following this 

 from October to December there is another maximum. Begin- 

 ning with December there is a slower growth, which reaches 

 its minimum in April. 



129876 517 



