INTRODUCTION 



brought into prominence. This is the Silver-grain or " felt," 

 which forms the beautiful flakes so much esteemed in Oak timber, 

 and which is composed of fragments of tissue called " medul- 

 lary rays." These, when seen on the end of a plank or on the 

 stump of a tree, resemble the radial strands of a spider's web 

 (See Frontispiece), a resemblance which is heightened when 

 the annual rings are prominent enough to simulate the cross- 

 bars of the we\|. As the rays proceed from the centre out- 

 wards it is only in those cuts which follow a radial direction 

 that is, in " quartered" timber that they appear at their best, 

 but they may be seen on the sides of boards, becoming bolder 

 and bolder the nearer the plank is to the heart, until upon the 

 centre plank they occupy so large a proportion of the surface 

 as to make it seem a different kind of wood to the neighbour- 

 ing planks. 



It must not be supposed that all woods share this feature in so 

 great a degree as the Oak ; on the contrary this valuable figure is 

 obscure in most species and frequently needs careful search to 

 find it. 



There is, however, no wood in which it may not be found. 

 There are some kinds which do not show the annual rings, 

 others which lack other features present in the Oak, such as 

 the pores or the soft tissue ; but none of the Conifers, or of 

 the Broad-leaved trees, can be found without these rays or 

 silver-grain (see Plate xxiii.). 



The pores just mentioned are the little grooves seen upon the 

 surface of cut planks which give to them the appearance known 

 as " coarseness of grain." They are little tubes technically 

 called " vessels " whose openings can be seen at the end of a 

 plank (transverse or horizontal section) closely arranged in the 

 annual ring in various ways. The pores become smaller and 

 smaller as they approach the Autumn or outer boundary, until 

 they seem to disappear from very tenuity and, both " plankwise " 

 and " across-grain," require a lens to follow them. In the 

 Oak (see Frontispiece), which is the easiest and best example, 

 these smaller pores are arranged in little tree-like patches, im- 

 bedded in a mass of light-coloured soft-tissue. This is composed 

 of short, thin-walled cells unlike the mass or ground tissue of 

 the wood, which is chiefly built up of long spindle-shaped fibres 

 with thick, woody walls, imparting the qualities of hardness 

 and tenacity to the timber. The soft- tissue, on the other 

 hand, lacks these properties, but has a peculiar significance, 

 inasmuch as it is frequently the character which declares to 

 which division or group the wood belongs. The conspicuous 

 " pore-ring," the character which most strikes the eye in many 

 woods, has but a trifling value in this respect, for there are 



xv 



