Tree."? — The Character, S^ivncUire^ Sec. 47 



wood, on the other hand, no longer performs the phj^siological 

 function of condncting water and serves the tree only as a 

 mechanical support. 



Sometimes the boundary of the sapwood in the felled trunk 

 is indicated by the discolouration bronght about by fungi and 

 other agencies, but this in no way prolongs its life as timber, 

 unless it has been subject to an antiseptic treatment after being 

 seasoned. The number of rings over which the sapwood extends 

 is not thn same in all trees, nor even in the same si)ecies of the 

 same age. 



The sapwood may be sharply defined from the heartwood 

 as is the case in Yew and Robinia, or they may gradually merge 

 one into the othei'. 



The presence or absence of heartwood is not characteristic 

 of all the species belonging to a single gerius. In the Aspen 

 Poplar there is no heartwood, while the White and Black Poplars 

 have heartwood. Similarly the European Bii'ch is a sapwood 

 tree, while the American Birch is a heartwood tree. Other 

 examples of sapwood trees are Hornbeam, Sycamore, Alder and 

 Lime. 



hiteinal Sapwood. — Douglas Fir and Oak sometimes show 

 among the rings of coloured heartwood some colourless zones 

 which are liable to decay. In the Oak s]-)ecimen exhibited it 

 should be noted how this colourless portion embedded in the 

 darker heartwood has become attacked by Anobids while 

 the heartwood remains untouched. These zones constitute what 

 is known as " internal sapwood " and, like the outer sapwood, 

 will take preservative treatment. 



Internal Bark. — Sometimes at the butt end of the log there 

 is an internal bark which also causes a defect. This is due to 

 the fusion of vertical shoots while young, the numl^er of shoots 

 present being indicated by the number of piths. Higher up the 

 trunk there will be only one centre, due to the additional conical 

 layers of wood enclosing the young shoots. In the specimen of 

 fjime exhibited there are two piths shown. 



