54 GUIDE TO TIMBERS OF NIGERIA 



Uganda, do not agree either with the present or with the 

 following species. 



GENERAL CHARACTERS. A soft, light wood of an oatmeal 

 colour with darker striations (pores) in longitudinal section. 

 The colour deepens little if at all. Surface distinctly dull, 

 warm to the touch, dry, soils readily. The shade of the trans- 

 verse section depends upon the satiny pile which covers the 

 surface. Smell, none. 



Unwin says (1920, p. 438), " hard, light yellow, and close- 

 grained." 



STRUCTURE. Transverse section. (Prepared with a corundum 

 hone and pumice-stone, but the silky pile cannot be removed 

 by any known means.) See PI. IV, fig. 5. 



Parenchyma of one kind : (a) vasicentric, easily visible to the 

 unaided eye as sheaths around the pores by its darker colour 

 (a rare feature) ; often joins the pores into festoons which 

 anastomose freely ; width at least equal to the long diameter 

 of a large pore ; there are about 10-12 of these lines in a wide 

 ring and they occur in all zones ; proportion of the wood about 

 one-fifth. 



Vessels visible as perforations, especially in the darker wood ; 

 large, diminishing slightly but regularly in size towards the 

 boundary of the ring, not decreasing in numbers ; 2-10 per 

 sq. mm. ; very evenly distributed ; simple or in radial 

 groups of 2-3 pores, the latter rare ; widely isolated ; shape, 

 oval. 



Rays just visible with the macroscope and then solely on 

 account of their colour, which is the same as that of the P. (a) ; 

 very fine indeed ; of one kind ; regular in size and spacing, 

 about three to the pore-diam., and avoiding the pores ; much 

 resembling silk threads ; 12-18 per mm. ; proportion of the 

 wood about one-fourth. 



Ground-tissue-cells visible with macroscope; they ncnll 

 strings of beads and probably contain crystals. 



Rings very sharply defined ; boundary a dark line which 

 is the only portion of the wood where the tissue is darker than 

 the rays, elsewhere it is much lighter ; contour undulating in 

 long waves as in the European Hornbeam (rare case). 



Radial section. Rather more lustrous and silky than the 

 other sections. Grain empty. P. (a) visible with lens on 



