GUIDE TO TIMBERS OF NIGERIA 61 



but is entirely different from that of the common Opepe (Sarco- 

 cephalus esculentus). 



Transverse section. (Prepared with glass-paper.) 



Parenchyma of three kinds : (a) narrowly sheathing the 

 vessels, very pale yellow in colour ; (b) in excessively fine bars 

 from ray to ray and if anything finer, at intervals about equal 

 to the space between the rays, practically absent from the 

 denser zones, colour nearly the same as the rays ; (c) terminal, 

 simulating the boundaries of the rings, but only occasionally 

 visible and readily overlooked on account of lack of contrast ; 

 a very narrow line a little finer than the rays. 



Vessels just visible as perforations (on clean-cut section), 

 small, diminishing slightly towards the outer edge of the ring, 

 uniformly distributed except in the dense zones where there 

 are few if any, scattered in no particular order ; number per 

 sq. mm. 1627. There is a tendency for the vessels to run 

 into straggling lines in various directions ; mostly single, some 

 groups of 2-3. Shape, broadly oval. Contents, white masses. 

 Proportion of the area of the section (including their paren- 

 chyma) not more than one-sixth. 



Rays visible with lens, very fine, of one kind, fairly regular 

 in size and spacing at intervals of rarely more than twice their 

 own width, very numerous ; proportion of the mass of the 

 woods at least one -third : number per mm. 14-18. 



Ground -tissue-cells visible with the macroscope, their 

 contents (crystals ?) showing as white points ; proportion of 

 the mass about one-third. 



Rings apparently well defined, but no definite boundary unless 

 indicated by the dense zones or the line of parenchyma (c). 



Radial section. Rays just visible by reflection as fine lines. 

 Parenchyma (a) readily visible as very fine borders and tails 

 to the vessels ; P. (c) rarely appears. Vessels, very fine grooves 

 just visible, except where their white contents make them 

 more prominent. Besides the white contents there are some 

 reddish-brown globules here and there. 



Tangential section as the radial, but the vessels seem rather 

 more prominent on account of cross-grain. Rays very minute 

 and obscure spindle-shaped lines visible with the macroscope, 

 up to sixteen cells high and 1-3 wide ; not in parallel. With 

 a high power many brown globules are to be seen. 



