14 FUSTIC WOOD: ITS SUBSTITUTES AND ADULTERANTS. 



pits. Crystals of calcium oxalate are exceedingly abundant in wood- 

 parenchyma fibers/ especially in cells bordering pith rays. These 

 polygonal crystals occur in perpendicular rows varying from few to 

 8 or 10. 



Pith rays 2 are regularly distributed throughout the wood. They are 

 from 1 to 3 cells wide and from few to 30 or more cells high. They 

 range in height from 0.2 to 0.7 millimeter. In a tangential section 

 the pith-ray cells may be observed to vary considerably in size. 

 Within the layer of denser tissue the rays are very narrow and the 

 cells are invariably compressed laterally; within the bands of wood- 

 parenchyma the pith rays are broader and the ceils composing them 

 larger and perfectly round in transverse sections. Ray cells border- 

 ing wood-parenchyma fibers occasionally contain crystals of calcium 

 oxalate, but these crystals, very numerous in this wood, are found 

 mainly in wood-parenchyma fibers. The individual cells of such 

 fibers are cubic, and are usually much larger than the ordinary wood- 

 parenchyma cells. The sculpture of the walls of the pith-ray cells 

 is similar to that of the cells of the wood-parenchyma fibers. 



1 Parenchymatous ebments containing crystal are known as idioblasts. 



2 See description (fig. 1). 



O 



