ECONOMIC WOODS OF THE UNITED STATES 



17 



Taxus, and Tumion, the tracheids are characterized by spiral 

 thickenings on the inner wall. 



TABLE I 



LENGTH OF TRACHEIDS IN CONIFEROUS WOODS 



In certain conifers, particularly Pinus, specialized forms of 

 tracheids of a parenchymatous type are found associated with 

 resin ducts and cysts. They resemble wood-parenchyma cells in 

 form and function, but have bordered pits hi their side _and end 

 walls. " Resinous tracheids" are ordinary tracheids with deposits 

 of resin usually in the form of thin transverse plates. 



The tracheids of broadleaf woods (Fig. 2, E) are subordinate 



