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 



Botanical Name 



Abies balsamea 



" concolor 



" grandis 



Chamsecyparis lawsoniana 

 " thyoides . . 



Larix occidentalis 



Libocedrus decurrens .... 

 Picea engelmanni 



" rubens 



" sitchensis 



Pinus echinata 



" edulis 



" lambertiana 



" monticola 



" murrayana 



" palustris 



" ponderosa 



" resinosa 



" strobus 



" tseda 



" virginiana 



Pseudotsuga taxif olia .... 



Sequoia sempervirens .... 



" washingtoniana. . 



Taxodium distichum 



Thuya occidentalis 



" plicata 



Tsuga canadensi.s 



" heterophylla 



2.00 

 2.75 

 2.90 

 2.55 

 1.45 

 1.75 

 3.00 

 3.05 

 2.50 

 2.30 

 4.40 

 1.50 

 2.75 

 2.75 

 1.80 

 3.00 

 2.50 

 3.20 

 3.20 

 2.55 

 1.75 

 1.80 

 4.05 

 3.45 

 3.65 

 1.40 

 3.15 

 2.80 

 1.75 



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 in 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 subordinp.te 



