70 



FABRIC OF PLANTS. 



Slice from the root of the date tree, magnified. a, straight tube ; 

 6, modified vessels or air -tubes of Link; c, straight vessels; d, 

 air- tube of Link. 



The Silver Grain. 



The beginner must take care not to confound with 

 the fibrous tissue, which runs perpendicularly, those 

 woody rays running out from the centre of trees, and 

 termed by carpenters the silver grain l ; for though 

 this gives firmness to the plant as the fibres do, it is 

 wholly composed of cellular tissue, which has been 



(1) In Latin, Radii medullaris. 



