336 The Philippine Journal of Science 192s 



idioblasts very numerous and prominent, often making up the 

 whole ray. Wood rays small (3 by 30 to 40 cells) ; infiltration 

 sparse. 



Remarks. — Used for permanent construction such as houses, 

 bridges, wharves, and railroad ties owing to its great strength 

 and durability. Often mistaken for Vatica but distinguished by 

 the concentric rows of resin cysts and diff use-zonate parenchyma. 



Hopea plagata is very widely distributed in Luzon, from 

 Cagayan southward to Sorsogon. Also reported from Mindoro 

 southward to Basilan. 



ISOPTERA BORNEENSIS Scheffler. Malayakal. (Plate 26.) 



Gross features.— Sapwood light gray, medium thick; heart- 

 wood pale grayish to yellowish gray. Wood fine to medium 

 textured, cross grained, hard to very hard, heavy to very heavy; 

 specific gravity, 0.734? 



Microscopic features.— Vessels numerous, medium sized, 44 

 to 250 n (average, 180) in transverse section, rounded to oblong, 

 thick walled, solitary or in groups of 2 to 4 ; tyloses very prom- 

 inent, completely occluding the pores. Tracheids numerous 

 but less so than in Parashorea. Fiber tracheids absent. Libri- 

 form fibers numerous, medium-sized (18 to 1,480 /.), with walls 

 8.3 p in thickness, in indistinct radial rows. Vertical idioblasts 

 present. Horizontal idioblasts wanting. Rays small (4 by 35 

 cells). Organic infiltration conspicuous. 



Remarks.— A very strong and durable wood, and for this 

 reason largely employed in permanent construction where 

 strength and durability are essential. Used for the same 

 purposes as Hopea plagata, and probably the source of the 

 bulk of the yakal timber of the market. 



Isoptera borneensis is reported from Camarines, southern 

 Luzon, southward to Samar and Mindanao, where it forms 

 extensive stands in Zamboanga. 



SHOREA BALANGERAN (Korthals) Dyer. GlSOK. (Plate 27.) 



Gross features.— Very similar to malayakal. Sapwood light 

 gray, medium thick; heartwood grayish to yellowish gray. 

 Wood fine textured, cross grained, hard to very hard, heavy to 

 very heavy; specific gravity, 1.05. 



Microscopic features.— Vessels scattered, small, 73 to 191 /* 

 (average, 138) in diameter, rounded to oval, solitary or in 

 groups of 2 or 3; tyloses numerous. Tracheids few, 1 or 2, 

 proximate to vessels. Fiber tracheids wanting. Libriform 

 fibers numerous, small (18 by 1,480 ,*), with walls 7 ^ in thick- 



