GUIDE TO TIMBERS Of* NIGERIA 18 



lines about equal to the smaller spaces between the rays and 

 at intervals of about lj times to twice their own width ; equally 

 abundant within any apparent ring, but occasionally inter- 

 rupted by a denser zone which may be the limit of the ring ; 

 proportion of the mass of the wood (including the vessels) about 

 one-quarter. 



Vessels readily visible to the' unaided eye as perforations 

 apart from their parenchyma, very large, apparently not 

 diminishing in size ; variation in numbers little, except in the 

 dense zones ; number per sq. mm. 58 ; a tendency to an 

 arrangement in echelon, otherwise they are widely isolated ; 

 oval ; mostly empty. 



Rays on the limit of vision, very fine ; colour as the paren- 

 chyma, but slightly darker ; of one kind only, multiseriate, 

 straight : number per mm. 5-8 at intervals of about their own 

 width to that of a pore, and irregularly spaced ; fairly regular 

 in size ; proportion of the mass of the wood between one- 

 quarter and one-fifth. 



Ground -tissue -cells readily visible with the macroscope ; 

 proportion of the mass rather more than one-third. 



Rings apparently defined by the denser zones ; contour 

 regular. 



Radial section. Vessels very coarse, open and empty, having 

 loculi readily visible to the naked eye, size of vessels equal to 

 those of the Common Oak ; linings bright : the macroscope 

 shows very regular pitting in the vessels where they are in 

 contact with the rays. Parenchyma (a) appears as hoary lines 

 and as borders to the vessels. Rays inconspicuous, but visible 

 as minute hoary flakes, more so by reflection. Grain rather 

 oblique. 



Tangential section as the radial, but the rays are visible with 

 difficulty by reflection owing to their lack of lustre. They 

 are minute spindle-shaped lines up to about T \r inch high and 

 whitish in colour. Parenchyma very distinct in certain lights 

 in hoary lines and zigzag tracery. 



Pith? 



SAP WOOD well but not sharply defined from the heartwood, 

 colour pale buff or dirty white (about 1 to If inches wide in 

 specimen). Exterior of the log striated, due to the vessels 

 which are salient. 



