MICROSCOPIC OBJECTS. 33 



Fig. 65. Transverse Section of Alder-wood (Alnus 

 glutinosa) , x 200. Exogen. 



The large ducts of this wood were mentioned in the pre- 

 ceding description; their transverse sections are well illus- 

 trated by this drawing. The smaller holes represent the 

 transverse sections of the ordinary prosenchyrnatous tissue; 

 there are also a few parenchymatous cells. The dark lines 

 represent the transverse sections of the medullary cells. 



Fig. 66. Longitudinal Section of the Wood of the Willow 

 (Salix alba), x 120. Exogen. 



This wood also has rather large ducts ; and in this case they 

 are very numerous. The ordinary prosenchymatous tissue is 

 rather closely packed, and the medullary cells are small and 

 few in number. This wood being of such a light, open, yet 

 strong and durable nature, makes it extremely useful where 

 great elasticity and lightness are required, such as in boat- 

 building, cooperage, basket-manufacture, &c. A valuable 

 tonic medicine called Salicine is extracted from the bark of 

 this wood; its properties are nearly allied to those of 

 quinine. 



Fig. 10 represents a more highly magnified section of this 

 wood. 



