Dixon — Mahogany, Recognition of some Different Kinds. 457 



two or three times as tall as inner marginal cells ; acute, and often with 

 crystals. Inner cells small, with rounded or angular lumina. 



U.S. — Marginal cells of rays square, or polygonal and isodiametrical. 

 Fringe formed of palisade-like cells. 



Entandrophragma 0. DC. Also called Pseudocedrela (Sprague (15)), 

 African, and Sapeli (or Sapele) mahogany. 



C.S. — Parenchymatous laminae close, 3 mm-0'5 mm. or less apart; usually 

 more crowded in outer region of growth zones, sometimes forming undulating 

 discontinuous lines. — Circumvasal parenchyma often 3 or 4 cells thick, and 

 spreading tangentially. — Vessels isolated, or in radial pairs. Small groups 

 rare. — Fibres moderately thick, polygonal. 



T.S. — Rays 1-4-ply. Margin 1 cell thick, triangular, often inconspicuous. 

 Inner cells of small diameter usually fairly thick-walled. 



R.S. — Marginal cells of rays square or horizontal oblongs, not palisade- 

 like. 



Aucoumea Pierre. Also called Gaboon mahogany and Okoumie Wood. 



C.S. — Parenchymatous laminae rare or absent.— Circumvasal parenchyma 

 narrow, often filled. — Vessels isolated, in radial pairs or in small radial groups, 

 sometimes with tyloses. — Fibres thin-walled, nearly rectangular, with 

 tangential walls parallel, forming alternate zones of dense and more open 

 tissue (in which the lumina are reduced and enlarged respectively) gradually 

 passing into each other. 



T.S. — Eays 1 -, 2-, 3-ply. Margin, 1 cell deep. 



R.S. — Margin of rays 1 cell deep. Cells palisade-like, often rhomboid. 

 Walls often thick and pitted. All cells usually with transparent colourless 

 concretions and sometimes with dark deposit. 



The specimens of woods furnished by Khaya spp. may be distinguished 

 into four types, according to their microscopic structure : — 



Type 1 — Khaya anthotheca. — Occasional parenchymatous laminae, some- 

 times forming thick layers. No scattered parenchyma. Pays about 25 in 

 a 2-mni. field T.S. Average height of 5-6-ply rays = - 70, rising to TO mm. 

 Width of 5-6-ply rays about 0-084 mm. PI. XXX., figs. 52, 53. 



Type II — KJiaya senegalensis — Parenchymatous laminae rare. No scattered 

 parenchyma. Pays 30-50 in 2-mm. field T.S. Average height of 5-, 6-ply 

 rays = 0-45, rising to 070 mm., rarely 1 mm. Width = O'Oo-OTO mm. 

 Pis. XXX., XXXL, and XXXII., figs. 49, 50, 51, 55, 56, 57, 64, 65, 66. 



Type III — Khaya sp. ? (Axim). — Parenchymatous laminae rare. No 

 scattered parenchyma. Kays 40 in 2-mm. field T.S. Average height of 



4 c2 



