10-t JOURNAL OF FORESTRY 



In this connection it is generally conceded that the springwood part 

 of the ring is formed when the growth tensity is at its height, while 

 the summerwood is the result of sluggish growth towards the close 

 of the growing season. As a result, the springwood of the annual ring 

 is softer owing to the large size of the tracheary elements, their larger 

 lumina and thinner walls. Tracheid length shortens regularly during 

 the growing season until the outer layer of the summerwood is reached. 



In conclusion . it is of interest to note that the soft, light-colored 

 dipterocarps, namely, Sliorea c.viiitia, Pentacme spp., and Parashorea 

 malaanonan ofifer possibilities as a source of raw fiber in the manu- 

 facture of pulp and paper. One of the chief obstacles in the utiliza- 

 tion of hardwoods in paper manufacture is the shorter fiber length as 

 compared to conifers. In many cases, at least, this precludes their use 

 in the manufacture of paper, except as a filler with longer fibered, 

 usually coniferous, stock. Populus tremnloides, P. deltoides, and 

 P. grandidentata are at present the most important hardwood species 

 in the United States from the standpoint of paper manufacture. The 

 average fiber length of these species is 1.13 mm. as compared to the 

 light-colored dipterocarps enumerated above, which average 1.60 mm. 

 This would seem to indicate that Shorea eximia, Pentacme spp., and 

 other light-colored dipterocarp offer possibilities in the Philippines as a 

 source of raw fiber for the manufacture of paper when used either 

 alone or in admixture with bamboo, abaka (Manila hemp), maguey, 

 sisal, and other long-fibered stock. 



The writer wishes to express his sincere thanks to Prof. H. P. 

 Brown for helpful advice and guidance. 



