22,3 Reyes: Woods of the Philippine Dipterocarps 333 



Dense specimens from western Luzon exhibit broad rays (9 by 

 55 cells), while in light samples they are restricted in size 

 (4 by 45 cells). 



Remarks.— This species furnishes the bulk of the white lauaan 

 of the trade and is used extensively for rough construction, 

 cheap furniture, and other purposes when strength and dur- 

 ability are not essential. The better grades are undoubtedly 

 mixed with almon and bagtikan and reach the foreign market 

 as "Philippine" or "white mahogany." 



Pentacme contorta is widely distributed throughout the Archi- 

 pelago, growing in admixture with other dipterocarps and 

 forming heavy stands. 



THE YAKAL GROUP 



The yakal group comprises the harder and heavier dip- 

 terocarps belonging to the genera Hopea, Shorea, Balanocarpus, 

 and Isoptera, and is to be regarded as purely arbitrary. It 

 approaches most closely the manggachapui group but differs in 

 the greater weight, hardness, and durability, and the darker 

 color of its woods. The first two genera contain numerous 

 species and are represented in other groups. Only two species 

 of Balanocarpus and one of Isoptera are known to occur in the 

 Philippines, and these are wholly confined to the yakal group. 



Gross features.— Sapwood pale grayish white, variable in 

 thickness ; heartwood pale yellow when first exposed, turning to 

 shades of yellow, brown, or reddish brown. In addition Hopea 

 mindanensis and Balanocarpus cagayanensis exhibit greenish 

 streaks which assume the form of concentric bands. Wood 

 very fine to medium textured, straight or cross grained, hard 

 to very hard, and heavy to very heavy ; specific gravity, 0.80 to 

 1.20. 



Microscopic features. — Vessels very small to medium, 67 to 

 180 ft in diameter, terete to oblong in transverse section, solitary 

 or grouped; tyloses abundant, very conspicuous. Tracheids 

 present or wanting. Fiber tracheids wanting. Libriform fibers 

 numerous, thick walled, closely packed, radially or irregularly 

 arranged. Vertical parenchyma various, vasicentric to diffuse. 

 Resin cysts in interrupted concentric rows, relatively incon- 

 spicuous. Idioblasts present. Wood rays narrow to medium, 

 not exceeding 5 cells. Organic infiltration variable. 



Remarks.— This group comprises the hardest and most dur- 

 able of the Philippine dipterocarps, and furnishes the bulk 

 of the heavy structural timbers of the Islands. 



