272 R. T. BAKER. 



In the wood parenchyma are seen groups of (apparently) 

 broken cells. Tracing these back from a two or three 

 years' old twig, they are seen to be the phloem cells of the 

 bundles and stain purple, with haematoxylon, as with other 

 phloems. They are composed of thin walled bast paren- 

 chyma and bast stone cells, the latter showing the long 

 axis in the longitudinal section, and with comparatively 

 thin walls, both being filled with what is probably a tannin 

 substance. Combined they make up the remarkable 

 "dottings" on the outer edge of each concentric "ring," 

 which continue to appear almost regularly as the tree 

 attains maturity, and macroscopically examining a piece 

 of timber they appear as rows of pin pricks. I believe 

 these perform all the functions of the ordinary bark of a 

 dicotyledonous plant, as injury to the outer cortex has no 

 effect on the life of the tree. 



Tangential Section. — In this view, (Plate XLIII, figure 

 17) are clearly brought out the different angles or planes 

 in which the fibres run, and the sclerenchymatous cells are 

 seen to be exactly the same shape as in the transverse 

 section, showing that they are short, isodiametric bodies 

 and not elongated. It is due to this particular form that 

 the timber splits so readily tangentially, there not being a 

 length of fibre to give an interlocking strength, or in other 

 words no cross structure such as would occur if the rays 

 ran through and held together the annual "rings." The 

 phloem cells with the broken content (supra) are here seen 

 longitudinally. 



Radial Section (Plate XLIV, figure 18). — Owing to the 

 twisting of the wood fibres, it is almost impossible to get a 

 section showing the full height of a ray, which vary from 

 uniseriate to multiseriate, such as are seen in figure 17, 

 which shows conclusively how completely the vertical 

 sclerenchymatous ring of cells restricts them to the width 



