294 The Philippine Journal of Science 1923 



those anatomical features which may be considered as typically 

 dipterocarp. Furthermore, Parashorea malaanonan has been the 

 subject of numerous studies of growth and management in the 

 Archipelago, and a detailed study of its anatomical structure may 

 help to solve problems of its utilization. 



The remainder of the present study consists in a detailed 

 enumeration of the gross and minute anatomical features and 

 physical properties of the wood of the other commercial dipter- 

 ocarps, 8 employing Parashorea as a foundation for the technical 

 discussion. The anatomical departures will be noted at length, 

 and it is hoped that the keys which accompany the study will 

 prove of diagnostic and practical value. 



I take this opportunity to express my sincere gratitude to Dr. 

 H. P. Brown, head of the department of wood technology at the 

 New York State College of Forestry at Syracuse University, 

 Syracuse, New York, under whose department this piece of 

 work was performed. Doctor Brown tendered invaluable advice 

 and criticisms throughout its preparation. 



ANATOMY OF THE WOOD OF PARASHOREA MALAANONAN (BLANCO) 



The wood of Parashorea is numbered among those of the softer 

 dipterocarps and is moderately hard and moderately heavy 

 (specific gravity, 0.594) . 9 The sapwood, which is narrow and 

 seldom over 2 to 3 centimeters in thickness, is grayish white 

 when first exposed, but often assumes a dark brown hue 10 in 

 striking contrast to the paler, reddish brown heartwood. 



'Seventy-two species of Philippine dipterocarps are known to date, 

 grouped in nine genera. Of these, some twelve may be considered as 

 strictly commercial species and about an equal number are of more or 

 less importance locally. See Foxworthy, F. W., The Philippine Diptero- 

 carpaceae, Philip. Journ. Sci. § C 6 (1911) 231; 13 (1918) 163. 



* Determination based on mature trees from different localities ; wood 

 with moisture content of approximately 8 per cent. 



10 The darkening of the sapwood of Parashorea upon exposure to the air 

 is due to certain chemical (oxidative) processes which take place in the 

 wood. The vertical and ray parenchyma cells remain living as long as 

 they are a part of the sapwood, and contain varying amounts of organic 

 material. When a tree is felled and optimum conditions of temperature 

 and humidity prevail the enzymes which ape present in these living cells 

 bring about chemical changes in their contents with a resultant darkening 

 of the tissue. See Baily, I. W., Bot. Gaz. 50 (1910) 142-147. 



