PITH OF BROAD-LEAVED TREES. 29 



considerable variety among broad-leaved trees, so as to be used 

 to some extent in discriminating woods seen in complete cross- 

 sections. Thus in its proportion to the area of the wood in 

 cross-section it may vary from equality, i.e. being as wide as the 



FIG. 21. Tangential longitudinal section of Oak, magnified 50 diameters, 

 showing transverse sections of pith-rays. After Miilli-r, from The 0<tk, by 

 permission of Prof. Marshall Ward, and Messrs. Ki-^an I'aul, Trench, 



Trtlbnor & Co. 



xylem, as in three-year old shoots of Elder, to ^|^, as in shoots 

 of the Cork-Elm of the same age. In outline it may be pent- 

 angular or hexagonal, as in Oak, Spanish Chestnut, Black Poplar, 

 or White Willow ; triangular, as in Birch, Beech, and con- 

 spicuously in Aider; ovoid, as Linden, Plane, Holly, Ash, and 



