258 HISTOLOGY OF MEDICINAL PLANTS 



twenty cells in height according to the part of the medullary 

 ray bundle cut across. 



The medullary ray cells exhibit their height and length. 

 The walls of the cells are yellowish white and strongly 

 porous. 



Wood Parenchyma. The wood parenchyma cells have 

 yellowish, thin walls and blunt end walls. 



Wood Fibres. The wood fibres have thick, yellowish-white 

 walls, and the end of the cells are strongly tapering. 



TANGENTIAL SECTION QUASSIA 



The tangential section of quassia (Plate 106) shows the 

 following structure: 



Vessels. The vessels are very long and broad and the 

 yellow walls are marked with clearly defined pits. 



Medullary Rays. The tangential section shows the cross- 

 section of the medullary ray bundle and the cross-section of 

 the medullary ray cell. 



The medullary ray bundle varies in width from one to five 

 cells. The ends of the bundles are always one cell in width, 

 while the central part of the bundle is frequently five cells 

 in width. 



The medullary ray cell varies in size, structure, and shape 

 according to the part of the cell cut across. The cells cut 

 across the centre show hollow spaces, but the cells cut just 

 above or below the end wall show a strongly pitted surface. 

 The cells forming the end of the bundle are larger than the cells 

 forming the centre of the bundle. 



Wood Parenchyma. The wood parenchyma cells are greatly 

 elongated and the walls are thin and yellowish white. The 

 ends of the cells are blunt. 



Wood Fibres. The wood fibres are elongated, the walls 

 are thick and the cells are strongly tapering. 



In quassia, white sandalwood, red sandalwood, and guaiac 

 wood are characteristic crystals. 



In quassia the vessds are finely pitted, yellowish, and dis- 

 tinct; in white sandalwood the vessels are coarsely and sparingly 

 pitted and white translucent; in red saunders the vessels are 

 coarsely pitted, bright red and distinct. 



