OAK. 255 



The minute structure of Oak has already been to some extent 

 described and fully illustrated in Part I. The pith, at first 

 white, then brown, is pentangular and from 1 4 mm. across : 

 the pith-rays are of two kinds, very broad, lustrous, light- 

 coloured ones the "silver-grain" sometimes f in. apart, and 

 others, far more numerous about 300 to the inch very fine 

 and less straight. The annual rings undulate slightly, bending 

 outwards between the broad pith-rays : they vary in width from 

 1 8 or more millimetres, and they are conspicuous owing to the 

 pore-circle of very large vessels in the spring-wood, which is only 

 a single row when the rings are narrow or four rows when they 

 are wide. Into the autumn-wood there radiate outwards straight 

 or bifurcating bands of finer vessels, tracheids and cells (Figs. 

 19 and 27). Numerous, very narrow, wavy, peripheral lines 

 (" false-rings ") of wood-parenchyma, recognizable by their con- 

 tents, but seldom more than a single row of elements each, are 

 generally visible, especially when the annual rings are broad. 



Owing to the large proportion that the pores bear to the fibre 

 when the annual rings are narrow, such slow-growing unthrifty 

 Oak, growing on poor soil or in severe climatic conditions, is, 

 though often beautifully marked, softer than the broad-ringed, 

 thrifty, quick-grown wood of good soils and a favourable climate. 

 They may differ to the extent of their specific gravities a fair 

 criterion of their hardness and strength varying from 691 to 

 827 respectively. 



Que'rcus Rdbur is a somewhat variable species, three somewhat 

 inconstant types being recognized as British, viz. pedunculdta, 

 sessilifldra and intermedia. Que'rcus Rdbur pedunculdta derives its 

 scientific name from the long stalks to its acorns, for which 

 reason also the Germans call it " Stieleiche," whilst from the 

 situations in which it grows they call it " valley oak " (Thaleiche), 

 and from its early production and shedding of its leaves it is 

 called " early oak " (Friiheiche) and " Sommereiche." It is 

 generally quick-growing, but does not, perhaps, produce so great 

 a length of clear stem as sessilifldra. Its wood may be lighter in 

 colour, whence apparently it gets its French name, " Chene 



