MICROSCOPIC STRUCTURE 141 



applied to it the epithet 'pulcherrima,' 'very 

 beautiful.' It attains a height of 100 feet 

 and upwards, and is a native of Central Europe 

 and Northern Asia. 



Its timber is not so much prized as that of 

 some other species, but has the great advantage 

 of being durable under water. 



From its bark exudes a resin, which when 

 purified is known as ' Strassburg Turpentine.' 



The illustration (Pig. 42) is taken from a 

 photo-micrograph of 32 diameters; the focal 

 distance was 32 inches; and the objective 

 used was the 1-inch. 



It represents a section across a twig of the 

 Norway Spruce, Abies excelsa. 



Commencing at the outside edge we see the 

 thick cortical cells ; next we have the cellular 

 tissue with air cells, or air spaces; these lie 

 immediately under the cortical cells; in the 

 third layer we observe white spaces at inter- 

 vals in cellular tissue, these are resin canals; 

 further towards the centre and radiating in 

 marvellously beautiful lines closely packed 

 together, are the woody fibrous vessels ; inside 



