OF WOOD IN GENERAL. 



deposit of a spiral thickening band internally, or of a series of 

 rings, and, in the case of tracheae, the absorption of the trans- 



9 











p.v. 



FIG. 10. Elements of Oak wood, highly magnified. /, fibre ; to.p, part of 

 row of wood-parenchyma cells; tr, tracheid ; p.v, trachea (part of); sp, part 

 of a spiral vessel. From The Oak, by permission of Prof. Marshall Ward and 

 Messrs. Kegan Paul, Trench, Trtibner & Co. 



verse walls of the vertical rows of cells. Whilst tracheids are 

 elongated cells, losing their contents, generally becoming lignified 

 and having thickened walls, so as to be adapted for the conveyance 



