334 The Philippine Journal of Science 1923 



Key to the genera and species in the yakdl group. 



1. Wood when freshly cut greenish or with grass green streaks 2. 



Wood neither greenish nor with grass green streaks when freshly cut..3. 



2. Wood when freshly cut reddish, aside from the greenish streaks; pores 



medium (average, 159 /*) ; rays large, 4 by 95 cells; southern species. 



Bagususu (Hopea mindanensis). 



Wood when freshly cut grayish or yellowish green to grayish brown, 



aside from the greenish streaks; pores fine (average, 119 **) ; rays 



small, 4 by 25 cells; northern species. 



Narek (Balanocarpus cagayanensis) . 



S. Texture very fine; pores small (average, 100 M-), indistinct to the naked 



eye; wood very hard and very heavy; specific gravity, 0.98 to 1.20; 



tracheids and vertical idioblasts wanting Yakal (Hopea plagata). 



(average, over 100 m), 



very hard, heavy to very 



tracheids and vertical idioblasts 



(average, 180 /*), conspicuously thick walled; tracheids 

 and vertical parenchyma prominent; tyloses completely occluding the 



vessels Malayakal {Isoptera borneensis) . 



Pores small (average not over 140 a»), not conspicuously thick walled; 

 tracheids and vertical parenchyma not prominent; tyloses not com- 

 pletely occluding the vessels Gisok (Shorea balangeran). 



HOPEA MINDANENSIS Foxworthy. BagAsusu. (Plate 29, fig. 2.) 



Gross features.— Sap wood grayish white, subject to sap stain, 

 thin; heartwood reddish brown with concentric greenish zones 

 which turn nearly black with age. Wood fine to medium 

 textured, fairly straight grained, very hard and very heavy; 

 specific gravity, 0.849. 



Microscopic features.— Vessels numerous, medium-sized, 37 

 to 191 fx (average, 159) in diameter, ovoid in transverse section, 

 solitary or in groups of 2 or 3 ; tyloses numerous. Tracheids 

 and fiber tracheids wanting. Libriform fibers numerous, small 

 (19 by 1,566 ^), with walls 8.3 M in thickness, radially arranged. 

 Vertical parenchyma vasicentric- and diffuse-zonate, in tangen- 

 tial bands, connecting wood rays. Resin cysts in interrupted 

 concentric lines. Horizontal and vertical idioblasts present, the 

 last predominating. Wood rays medium (4 by 95 cells) , dark 

 colored with organic infiltration. 



Remarks.— Used locally for structural timber, railroad ties, 

 bridge construction, and other purposes where a strong and 

 durable wood is required. Similar to narek but can be distin- 

 guished by the reddish tinge of the wood. Probably more 

 durable than the manggachapuis although less lasting than the 

 better-known yakals. Easily distinguished from the other 



