KIliKK STUDIUS Ol' 1)1 l'Ti:U( )CAl<l'S 101} 



as well as within the species providing the wood exhibits varying degree 

 of hardness. This would seem to indicate that other things being equal, 

 the fiber length of dipterocarp wood varies indirectly to the density. 



An interesting variation is found in woods of like den.sity where 

 pores vary decidedly in size. The figures indicate that other things 

 being equal, fiber lengths are directly proportional to the size of the 

 pores. This was strikingly illustrated in Shorca eximia, where a num- 

 ber of specimens of practically the same density and hardness were 

 available for study. In the sample (40) the vessels were most re- 

 stricted in diameter, while (39) had somewhat larger vessels, and 

 specimen (38) showed the maximum width. The corresponding fiber 

 lengths were respectively 1.48, 1.64, and 1.78 mm., indicating a relation 

 between size of pores and fiber length. A like situation is found in 

 other dipterocarp species such as Anisoptcra tliurifcra, Pcntacmc min- 

 danaciisis, Shorca palosapis, and a few others. One exception was 

 noted to the above, namely, that of Shorca polyspcrma (55), which 

 was collected in the western coast of Luzon. This specimen possessed 

 smaller vessels and denser wood, but was the longest filtered of the 

 three species studied. 



A similar variation between fiber length and size of pores is likewise 

 found in diflferent species of the soft, light-colored dipterocarps, com- 

 monly designated as "white lauans." Within the "white lauan" group 

 there apparently exists a second distinct sub-group which is charac- 

 terized by wood of pale yellowish color and much finer pores. Included 

 here are Shorea pallida, S. polita, S. phillppiiicnsis, and S. mindancnsis, 

 and undoubtedly a number of less known species. The fiber length of 

 these forms average 1.10 mm. as compared to typical lauans, whose 

 fiber lengths average 1.60 mm. 



Bailey and Tuppen ^ have found that abnormal or depauperate plants 

 tend to form shorter fibers than normal individuals. This was found 

 to be the case in dipterocarps, since wood specimens from fast growing 

 species or individuals generally possess larger pores and longer fibers 

 than those of slower growth. This is analogous to the observations 

 of Miss Gerry,^ who found that the springwood of certain coniferous 

 trees possessed, as a rule, longer fibers than the denser summerwood. 



' Bailey, I. \V. and Tupper, W. W. "Size \'ariation in Tracheary Cells." 

 Proceedings of the Anier. Acad, of Arts and Sciences, Vol. 54, No. 2, Sept., 1918. 



'^ Gerry, Eloise. "Fiber Measurement Studies, Length, Variation : Where 

 They Occur and Their Relation to the Strength and Uses of Wood." Science, 

 Vol. 41 :179, 1915. 



