310 The Philippine Journal of Science 1923 



protoplasts as long as they are a part of the sapwood. Such 

 spaces are seen to advantage in cross section, particularly in 

 the libriform tissue, as minute chinks at the corners where 

 three or more cells meet or in tangential sections where wood 

 rays and vertical elements are coterminous. Such spaces are 

 of undoubtedly physiological significance in the life economy 

 of trees, but are often overlooked in a study of the wood owing 

 to their reduced size. 



COMPARATIVE ANATOMY OF THE MORE-IMPORTANT DIPTEROCARP 



In the following pages are incorporated the results of an 

 investigation into the comparative anatomy of dipterocarp 

 woods and their microscopic features. The Philippine species 

 have never been subjected to a comparative microscopic study, 

 and the present paper embodies much needed anatomical and 

 taxonomic data. I plan to supplement this information by sub- 

 sequent contributions as my knowledge of the woods of this 

 important family increases, and desire the present work to be 

 considered only in the nature of a preliminary survey. 



To one whose studies have been confined to the timbers of 

 the Temperate Zone, the most striking feature of dipterocarp 

 wood is the absence of distinct growth rings. The annual 

 zones so characteristic of extratropical woods are wanting, 

 owing to the fact that dipterocarps are evergreen trees of the 

 tropical rain forests and growth is practically continuous 

 throughout the year. Their wood when viewed in transverse 

 section at low magnification is seen to consist of tracheids and 

 parenchyma, traceable to fluctuating growth intensity. The 

 faint lines delimiting the growth rings of the diffuse porous 

 woods of the temperate regions are wholly wanting; the wood 

 is characteristically diffuse, but diffuse in the sense of being 

 homogeneous. 



The woods of this family are further characterized by the 

 presence of resin cysts, a feature which is diagnostic for the 

 group. These consist in a series of tabular cavities which 

 extend vertically for long distances in the tree, possibly from 

 the roots continuously to the leaves, and appear in the majority 

 of cases as white lines, owing to the nature of their contents. 



