ALDER O.N. 6703 



ALDER 



Alnus glutinosa Medic. Betulaceae. 



A diffuse-porous brownish or ecru-coloured wood of medium hardness. 

 Rather plain unless the rare, pale straggling rays appear in radial section. 

 A sap wood tree. 



Transverse section. Boundary, a line of contrast in density between 

 the rings, sometimes very clear or may be very obscure. Contour crenate 

 (arched outwards), between the large rays, where a notch occurs: this is 

 large in proportion to the size of the ray. 



Parenchyma. Invisible with lens. 



Vessels small, just visible, diminishing in size regularly outwards to the 

 Autumn wood ; to the lens, apparently crowded and occupying much of 

 the section, but thinning out in the outer side of the ring: a tendency to 

 a radial disposition. 



Rays of two kinds, simple and compound : the larger rare and casual, 

 and sometimes absent over wide areas, at others in groups: dull and 

 obscure unless wetted : nodose at the point where they cross the bound- 

 aries. 



Radial section. Boundaries obscure or sharp in places: vessels just 

 visible, rays rare and dull, but very long and straggling when properly 

 exposed. 



Tangential section. As the radial, but the boundaries rather more 

 definite: the rays appear as brownish spindle-shaped bodies, which are 

 readily visible, but need looking for: height from one to many inches. 

 The smaller rays appear as a fine, but quite visible, brown secondary 

 silver-grain. 



May be confused ivith: May be distinguished by: 



Plane tree (large rays crowded Large rays rare: silver-grain 



occupy half the section: silver- (when well exposed) of widely se- 



grain very conspicuous and cover- parated flakes which are pale and 



ing much of the surface). straggling. 



Beech (silver-grain conspicuous Silver-grain as above, dull rays 



though small: rays bright and in tangential section, 1 inch or 



readily visible in all sections: in more high, 

 tangential section they are not more 

 than \ inch high). 



Pear (watery extract rich red). Watery extract very pale brown, 



nearly colourless. 



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