ECONOMIC WOODS OF THE UNITED STATES 47 



developed spirally twisted growth layers after the trees were 

 thirty to forty years old, when, unprotected by associated trees, 

 they were subjected to heavy winds. There is a further possibility 

 that some species have an inherent tendency to develop twisted 

 stems. In any event, when such stems are sawn the lumber is 

 cross-grained and usually unfit for use where strength is required. 

 The extent of the defect depends upon the pitch of the spiral. 



When the elements interweave and are not constant in one 

 general direction, wood is also said to be cross-grained, though 

 the term spiral grain or interlocked grain is more applicable. Often 

 this condition does not interfere with tangential splitting. Wood 

 with interlocked fibres is tough and not necessarily weakened, 

 but alwaj^s tends to warp and tuist in seasoning. Examples occur 

 in Nyssa, ^-Esculus, Liquidambar, and Eucalyptus. 



Wavy grain and curly grain result when the fibres undulate 

 but do not cross each other. When the undulations are large the 

 grain is said to be wavy; when small, curly. Usually the waves 

 are on the radial plane and tangential splitting produces a smooth 

 surface, sho^\^ng the grain to advantage. Such grain is common 

 in Acer, Msculus, Fraxinus, Prunus, and Betula. It is most 

 common near the roots and at the insertion of large branches. 



Silver grain is produced by quarter-sawing timber in which 

 the rays are sufficiently high to show readily on radial surface. 

 The appearance of the rays adds very materially to the value of 

 woods for cabinet work and furniture. Species which exhibit 

 conspicuous silver grain are Quercus (all species, but particularly 

 Q. alba), and to a less extent Platanus occidentalis, Fagiis amcricana 

 and Prunus serotina. 



Texture is a term which refers to the relative size, quality, or 

 fineness of the elements as affecting the structural properties of 

 a wood. Like grain, it requires qualifying adjectives to attain 

 specific meaning. The most common attributes of texture are 

 fineness and coarseness, evenness and unevenness. Coarse texture 

 applies to woods with many large elements, or the average size of 

 which is large, for example, Casianea, Gymnocladus, Sequoia. In 

 fine texture the opposite condition prevails, as in Juniperus, 

 yEsculus, Salix, Populus. 



Even texture or uniform texture are terms used to describe 

 woods whose elements exhibit little variation in size, for example, 

 Taxodium (Plate II, Fig. 1), Juniperus (Plate II, Figs. 3, 4), 

 Sequoia, jEscuIus (Plate VI, Fig. 5). Uneven texture applies to 



