328 The Philippine Journal of Science m* 



Typical specimens can be separated, owing to the coarser tex- 

 ture of the red lauaan as compared to tangile, but inter- 

 gradations often occur which make identification difficult. In 

 addition to the differences enumerated in the key (page 325), 

 red lauaan is more susceptible to the ravages of ambrosia 

 beetles; in fact, to such an extent that it is difficult to find 

 a board that is free from "pinholes." Red lauaan is one of 

 the species marketed under the trade name of "Philippine 

 mahogany." 



Shorea negrosensis is widely distributed from northern Luzon 

 southward to Agusan and is especially abundant in Negros, 

 where it forms heavy stands in association with S. polyspermia, 

 S. eximia, Pentacme contorta, and Parashorea malaanonan. 

 Foxworthy states that this species is probably the most abun- 

 dant of Philippine commercial timbers. 38 

 SHOREA POLYSPERMA (Blanco) Merrill. Tangile. (Plates 19 and 20.) 



Gross features.— Sapwood light red, similar to red lauaan 

 and tiaong; heartwood generally lighter 39 than red lauaan, the 

 harder grades occasionally with a dark purplish tinge. Wood 

 medium to coarse textured (finer than red lauaan) , cross grained, 

 soft to moderately hard, light to moderately heavy; specific 

 gravity, 0.575. 



Microscopic features.— Vessels medium to large, 191 to 294 p 

 (average, 226) in diameter, oblong or rarely rounded in trans- 

 verse section. Tracheids less prominent than in red lauaan. 

 Fiber tracheids wanting. Libriform fibers smaller than in red 

 lauaan, 25 by 1,470 p, with walls 2.5 M in thickness, arranged 

 in distinct radial rows. Vertical parenchyma vasicentric and 

 diffuse as in Parashorea. Resin cysts distinct, in interrupted 

 concentnc lines. Idioblasts wanting. Wood rays variable; 

 those of soft grades narrow and high (3 by 50 cells). Ray 

 parenchyma heavily impregnated with gummy infiltration prod- 

 ucts, comparable to that of red lauaan in this respect. 



Remarks.— Used for high-grade furniture, cases for musical 

 and scientific instruments, and aeroplane propellers. Accord- 

 ing to tests conducted at the Forest Products Laboratory *• at 



opecimens grown in western Luzon are occasionally dark red to reddish 

 brown and are often of greater density. 



"Heck, G. E., and Dennis, C. E., jr., Mechanical and physical properties 

 °ol ,oib S ' F ° reSt Products Laboratory, mimeographed November 



