HEARTWOOD AND SAPWOOD. 269 



different parts of the tree, and especially the heartwood, their 

 own peculiar and distinctive colour, aroma, and technical 

 properties. Some trees form a harder and darker-coloured 

 heartwood (duramen) of inert tissue, which is heavier, more 

 thickly stored with organic and mineral substances, and more 

 durable than the younger zone of sapwood (alburnum). 



It is through the sapwood that the sap ascends from the roots 

 to the crown of the tree for elaboration in the foliage ; and on 

 the descent of the elaborated sap through the cambium, part 

 of it is used in adding a new layer of sapwood to the already 

 existing sapwood, while part is also used in forming a new 

 layer of bark (liber) to the outer protective covering. If a 

 ring or girdle be cut through the sapwood into the heartwood, 

 the tree is at once killed, because the upward course of the 

 sap is completely arrested; but this operation is more or less 

 ineffective in trees where the sapwood shows little or no visible 

 change in the older and inner part of the stem (e.g., as in Birch, 

 Aspen, Lime, Alder, Maple, Sycamore, Plane, and Hornbeam). 

 The sapwood is usually softer and less durable than the heart- 

 wood ; and the smaller the proportion of sapwood in any log of 

 timber, the more valuable and durable the timber usually is. 



With regard to the presence or absence of a more or less 

 distinct heartwood, our timber -trees may be classified as 

 follows : 



Heartwood trees : Oak, Elm, Chestnut, Robinia, Larch, Pine, 

 Douglas Fir, Cypresses. 



Trees with Imperfect Heartwood : Ash, Beech, Willow, Poplar, 

 Horse-Chestnut, Spruce, Silver Fir. 



Sapwood trees: Birch, Alder, Maple, Sycamore, Hornbeam, 

 Lime, Aspen. 



Heartwood trees can easily be killed by ringing or girdling 

 them i.e., cutting through the sapwood into the heartwood. 



III. The Ornamental Properties of Timber are its colour, 

 lustre, grain, texture, and marking. When green or freshly 



