PITH OF BROAD-LEAVED TREES. 31 



an interrupted or chambered structure : in the Elder it soon dies 

 and disintegrates, leaving the stem hollow; whilst in young 

 stems of Elm the inner portion of it has thin walls and loses 



its protoplasm, whilst the outer part becomes thick-walled but 

 retains its cell-contents. 



The pith-rays of broad-leaved trees are in general far more 



