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 vessels 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. 
