22,3 Reyes: Woods of the Philippine Dipterocarps 327 



Idioblasts wanting. Wood rays 3 or 4 by 50 cells in transverse 

 section. 



Remarks. — Tiaong is probably the softest and most homogene- 

 ous of the lauaans. The wood is not well known at present, 

 but occasional lots reach the market from Sibuyan and are sold 

 as genuine tangile or a high-grade red lauaan. It is not durable 

 when exposed and should be used only for interior work where 

 it will last for an indefinite time. This species is widely dis- 

 tributed in Luzon but has been reported from only one place 

 in Mindanao (Agusan). 



The wood of tiaong is very similar to mayapis in general 

 appearance but differs in that the resin cysts contain white 

 amorphous deposits. It can be distinguished from tangile be- 

 cause it is lighter and softer and has smaller and fewer resin 



SHOREA NEGROSENSIS Foxworthy. Red lauaan. (Plate 18.) 



Gross features. — Sapwood as in Shorea teysmanniana; heart- 

 wood red, turning to brick red, the darkest of the lauaans. 

 Wood coarse to very coarse textured, cross grained, soft to 

 moderately hard, light to moderately heavy; specific gravity, 

 0.541. Red lauaan resembles the wood of Parashorea but is 

 coarser textured and more homogeneous as a rule. 



Microscopic features. — Vessels very large, 176 to 426 /i (aver- 

 age, 329) in diameter, oblong or rarely rounded in transverse 

 section, grouped or solitary; tyloses sparse as in Parashorea. 

 Tracheids three or four near the junctions of vessels, larger 

 than the adjoining wood parenchyma cells. Fiber tracheids 

 wanting. Libriform fibers numerous, large, 28 by 2,020 ^ with 

 wide lumina and walls 2.20 to 4.38 p in thickness, depending on 

 the density of the specimen, in regular radial series, simulating 

 the tracheid arrangement in coniferous wood. Vertical paren- 

 chyma vasicentric and diffuse, similar to Parashorea. Resin 

 cysts in interrupted concentric lines. Idioblasts wanting or 

 sparse (none found in sections studied). Wood rays 3 or 4 

 by 50 cells in transverse section, heavily impregnated with 

 gummy infiltration products. 



Remarks. — Used for medium and high-grade furniture, house 

 construction, and cabinet work. High-grade flitches are often 

 converted into veneer and utilized in the manufacture of piano 

 and phonograph cases. Not durable when exposed but lasts 

 well when protected from moisture. Red lauaan closely resem- 

 bles tangile and is often substituted for this wood in the market. 



