GUIDE TO TIMBERS OF NIGERIA 57 



in the m-and-d groups) ; colour, light brown. Proportion of 

 the wood, small. 



Parenchyma (b) only just visible with lens as regards the 

 individual lines, but their abundance makes them visible in 

 the mass very readily. It is arranged in concentric, much 

 interrupted lines, or rather in bars irregularly inclined between 

 the rays ; number of lines per (radial) mm. very variable, 

 9-15 where present, otherwise at intervals equal to a 

 little more or less than the spaces between the rays and fairly 

 regular except in the dark wood, where they are for the most 

 part invisible. They recall the P. (b) bars of the European 

 Walnut. Proportion of the wood about one- sixth. Very 

 absorbent, swelling much on moistening. Contents granular. 



Vessels just visible as perforations, size medium scarcely 

 diminishing in size or numbers outwards ; evenly distributed ; 

 914 per sq. mm. Simple or in groups of 25 ; (simple pores 

 few) ; widely isolated ; oval ; proportion of the wood, about 

 one-quarter (including P. (a) ). 



Rays visible with difficulty ; of one kind and very fine ; colour 

 as the P. (b), i.e. buff ; fairly regular in size and spacing, at 

 intervals of about three times their own width; number per 

 mm. 15-16 ; weak ; some thin ends, indeed, the rays seem to 

 become thinner in the dense wood. Contents dark and granular. 

 Proportion of the wood, about one-third. 



Ground- tissue-cells just visible with macroscope ; contents, 

 small granules. Rings apparently defined to the unaided eye, 

 but less so with lens ; contour regular. 



Radial section. Parenchyma (b) visible with the macroscope 

 with attention, as fine lines. P. (a) visible with lens. Rays 

 visible by reflection, with the unaided eye. The rays are 

 perhaps slightly lighter in colour than the ground and contain 

 much resin, chiefly of a reddish -brown colour. 



Tangential section as the radial, but the rays are minute lines 

 about twenty-five cells in height by 2-3 rows wide containing 

 many black granules. Not in parallel. 



Density, No. 3013, 0-826, or about 51 \ Ib. per cu. ft. 



Sarcocephalus esculentus, Afzel. Rubiaceae. Gen. No. 3000. 



Synonym. S. sambucinus, K. Schum. (see note to ' next 

 species). 



