SHAPE OF TREES. 



121 



of the volume of the bole to that of a cylinder of equal height 

 and diameter (at chest-height). Neumeister* gives the 

 following form-factors, that of the ideal cylinder being 

 100: 



Straightness of Bole. This occurs when the axis of the 

 tree runs in a straight line. If the axis of a tree is bent in a 

 single plane, or a branch and part of a stem have their 

 axes in one plane, valuable curved timber, or knees, may be 

 formed, as in oak timber for ship- or barge-building. If the 

 tree bends so that its axis is in two or more planes, it is of 

 little value. Conifers are usually straight ; spruce, silver-fir 

 and Douglas fir the straightest, then larch and pines. Among 

 broadleaved trees, the cherry, poplars, alder and sessile oak 

 are straightest, but beech grows straight in a dense wood, 

 and a mixture of beech with oak, sycamore, ash, etc., will 

 straighten the boles of these species in a remarkable 

 manner. 



Percentage of Heartwood. In all trees, heartwood is 

 formed after a certain age only, [two or three years for 

 sweet-chestnut, so that mere coppice-shoots of this species 

 have a large percentage of hoartwood, and are very durablo 

 when used for fencing. Mulberry, robinia, laburnum and 

 larch also produce heartwood in 3 10 years. Mathey states 

 that in oak, when grown as standards over coppice, the 



* Forst u. Jagcl. Kalerider." l'JD2. 



