ABNORMAL TISSUES. 151 



in trees placed in a free position after being in a dense crop, or 

 affected by wounds, disease, or pollarding, they may develop 

 into (epicormic) branches. In such mottled wood the main stem 

 need not exhibit any bushy external growth from the dormant 

 buds, and its condition may be recognisable only by reason of 

 the irregularity of the bark cracks, or by the scales of bark being 

 small. Such wood is very inferior for plank? and cloven ware, 

 but its beautiful structure renders its sale-price very high. 

 Mottled wood may occur in all species of trees, even 





Fig. is. Tr;i: 'ion of birch niottlc'l wood with numerous 



dormant shouts. This is commercially termed Swedish ' lily-wood." 



conifers (Figs. 48 and 49) ; it may be due to alternations of 

 colour (p. 14(5). 



Bird's-eye maple is one of the most valuable forms of 

 mottled wood ; it occurs in all species of maple, and is 

 specially beautiful and common in that of the sugar-maple 

 (Acer saccharinuni) (Fig. 49). Bird's-eye oak-wood from 

 pollard trees is often extremely beautiful and valuable. 



If the dormant shoots bifurcate and grow individually in 

 thickness in concentric layers, large knotty swellings are 

 formed, often of considerable size ; they are termed Burrs. 

 In small pieces such mottled wood, e.g., in walnut, birch and 

 alder, is valuable and in common use for small articles, 



K 2 



