Dixon — Mahogany, Recognition of some Different Kinds. 465 



e.g. No. 284, with 50 groups in 2-mm. field.) Often with tyloses. — Fibres 

 thin walled, nearly rectangular, with tangential walls parallel, forming 

 alternate bands of dense and of more open tissue. Circumvasal parenchyma 

 1 cell thick, often with contents. — Eays narrow, often dark. 



T.S. — Eays of varying sizes, irregularly arranged 35-40 in 2-mm. field. 

 Total width in 2 mm = 0L6-0-20 mm. Height of rays on average = 

 0-30-0-42 mm. Width about 0'04 mm. Rays 1-, 2-, (3-) ply. Margin 

 distinct, acute, without crystals, but there is usually a globular concretion 

 in each cell, and often a dark deposit. The inner cells are somewhat smaller, 

 often filled with dark substance or containing a globular concretion. 



R.S. — Fibres are septate. — Marginal cells of rays often palisade-like, 

 rectangular, or rhomboidal, often with thick pitted cell-walls, and containing 

 globular concretions and sometimes dark deposit. 



Note. — As will be seen from the naming of the foregoing samples, the 

 term " Gaboon mahogany " is very generally applied to the wood of Aucoumca 

 Haineana Pierre. The term " okume " or " okoumie " seems more generally 

 used on the Continent; and De Wildeman in "Plantes Utiles du Congo," 

 quoted by Howard (9), states that okume is produced by Boswellia Haineana. 

 Pierre (13) in his description of the species A. Haineana states the plant is 

 called Aucoume, near Libreville. " Libreville mahogany " is another name 

 for this wood in the market. 



"Gaboon mahogany " is used in a different sense by Mell (10), who states 

 it is yielded by Entandroiphragma pierrei Chevalier 



Famechon (5) distinguishes between Okoumie and Gaboon mahogany. 

 This latter, he says, is yielded by Surcocephnles diderrichi (Sarcowphahhs 

 didcrrichii Wildem.;. It has a ruddy yellow tint, with red brown veins. Its 

 density is 0'64 in the dry state. 



24. African walnut (Type I.). 

 No. 219, from commercial source, labelled " African walnut." 



Olive brown, lustrous, zoned light and dark, with occasional black layers 

 formed by deposit between cells of parenchymatous laminae; distinctly roey. 

 Parenchymatous laminae, usually widely and irregularly spaced (0-5 to 

 more than 3 - cm. apart), often with black deposit in intercellular spaces. 

 Sp. gr. = 0-64. 



C.S.— Vessels rounded, isolated or in small (2-10) radial groups. 

 M.T.D. = 0-20 mm., 12-30 in 2-mm. field ; often with dark contents. — Fibres 

 thick-walled, regular, 6-20 between rays. — Circumvasal parenchyma often 



4d'2 



