Reyes: Woods of the Philippine Dipterocarps 



The elements which make up dipterocarp wood, aside from 

 the fiber tracheids, 32 have been enumerated and discussed in 

 detail in this paper, and there remains but to point out the 

 variations as to size, number, and alignment as found in the 

 various genera and species. Dipterocarp woods, as is the case 

 in those of other families, exhibit many microscopic features 

 in common; and the anatomical differences that separate 

 genera and species and which have such an important bearing 

 on the physical properties of the wood are traceable to fluctua- 

 tions in size, number, and arrangement, rather than to kinds 

 of elements. 



The most obvious evidence of modifications in the anatomy 

 of the various dipterocarp woods is varying texture. The latter 

 is governed by the size of the vessels in the main, since the 

 fibrous elements in strictly diffuse porous woods of the diptero- 

 carp type are too small to have their fluctuations in dimen- 

 sions count for much in terms of texture. In discussing the 

 vessels of dipterocarps it has seemed advisable to adopt an 

 arbitrary classification governed largely by the magnitude of 

 variation in the diameter of the average pore, and the follow- 

 ing groups were finally evolved as the study developed. 



Vessels M 



Very small 50-100 



Small 100-150 



Medium 150-200 



Large 200-250 



Very large 250-400 



Vatica mangachapoi and Hopea plagata are representative 

 of the lower extreme and possess pores that average less than 

 100 /x in diameter. They are accordingly to be considered as 

 very fine textured and in addition are hard and heavy as well. 

 Shorea negrosensis and Shorea eximia typify the other extreme 

 and possess pores that average over 250 n in diameter; they 

 are among the coarsest of the Philippine dipterocarps. Between 

 these two extremes all gradations occur, a feature which is 

 responsible, at least in part, for the wide utility of the woods 

 of this family. 



" Fiber tracheids, as the term implies, are intermediate in type between 

 tracheids and libriform fibers and are wholly wanting in Parashorea 

 wood. They are longer than tracheids but still retain the bordered pit 

 which, however, is reduced in size and often somewhat attenuated. 



