THE DECIDUOUS OAKS G.N. 



THE DECIDUOUS OAKS 



For example, Quercus robur var. sessiliflora Salisb. Q. p&luncuhita Ehrh., 

 and others. Fagaceae. 



Ring-porous brown or reddish-brown woods with a conspicuous silver- 

 grain. Hard and heavy. Heartwood trees. Sapwood wide. 



Transverse section. Boundary, the pore-ring. 



Parenchyma of two kinds, (a) imbedding the vessels (vasicentric), 

 abundant and clearly visible. It unites the vessels to radial str< 

 Parenchyma (b) in concentric lines or narrow zones chiefly in the Autumn 

 wood, usually very obscure and needing a cleanly-cut section, and the 

 lens. [Compare the American Red Oak, where this parenchyma (b) is 

 very clearly shown.] 



Vessels coarse, in radial streams as above. They diminish greatly 

 and regularly in size outwards to the Autumn boundary. Thyloses 

 present in most species. 



Rays prominent, of two kinds, large (multiseriate), and small (uni- 

 seriate). The larger are very irregular in size and spacing, the smaller 

 regular and about the width of a large vessel apart. Colour of the large 

 rays brown, lighter than that of the fibres. 



Radial section. Boundaries very prominent and of coarse vessels. 

 Rays conspicuous as a silver-grain (or flower), which is lustrous or dull 

 according to the incidence of the light. Thyloses generally visible with 

 lens as debris in the grooves. 



Tangential section. Boundaries appear as coarsely- fringed loops: 

 rays long, brown, spindle-shaped bodies best seen in the Autumn wood 

 within the loops: height 1-2J inches or even more. 



May be confused with: May be distinguished by: 



Chestnut (rays need lens in all Rays visible in all sections espe- 



sections except the radial where cially the radial, 

 they are very minute flakes). 



Evergreen Oaks (no pore-ring). Prominent pore-ring. 



Elms (vessels in the Autumn Radial streams of vessels, 

 wood in concentric lines). 



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