SCOTS FIR G.N. 8309 



SCOTS FIR 

 Pinus sylvestris Linn. Coniferae. Abietinese. 



A rather soft whitish to whitish-brown wood striped boldly with 

 resinous-brown belts. In extreme cases it may be very nearly white (the 

 sapwood), or as dark-coloured and resinous as Pitch Pine. A sapwood 

 tree, but the heart is not apparent when freshly felled ; it developes, on 

 drying. Sapwood very wide. Watery extract nearly clear and limpid : 

 potash causes little change : with perchloride of iron, clear brown solution 

 (constant?). 



Transverse section (compare Fig. 1). Boundaries always very well 

 denned by the more resinous Autumn wood on the outer side of the ring. 

 Contour regular. 



Pores or vertical resin-canals present, but never in the innermost zone 

 of the ring (i.e. the side towards the pith). The resin-canals are abundant 

 in the dark hard Autumn wood and occasionally stray a little beyond it into 

 the softer wood in the middle of the ring but this is quite exceptional in 

 our species. The lining-cells or epithelial-cells which clothe the interior 

 of these canals, is thin- walled in comparison with those of the Spruce, 

 i.e. less in thickness than the wal^s of the tracheids surrounding the 

 canals. 



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

 tangential section below. 



Ground-tissue of tracheids having bordered pits. 



Pith large, up to about fy inch, grey or brown. 



Radial section (compare Fig. 6). Rays very inconspicuous. Under 

 the microscope they are seen to be composed of two kinds of cells, the 

 uppermost and lowermost are tracheids having very jagged walls. The 

 middle cells (generally in several rows), are of parenchyma. They cross 

 the vertical tracheids of the ground-tissue at right angles and the point 

 where their walls mutually mark off a minute rectangular space is called 

 the "cross-field.". In the cross-field of this species there is a large simple 

 (unbordered) pit of a somewhat rhomboidal shape, which occupies 

 practically the whole of the available space. Very occasionally there 

 may be two such pits present, but they are exceptional and very rare. 

 This point must be grasped, as the number and size of these pits in the 

 cross-field form one of the very scanty points dappui that we have for 

 distinguishing the various genera of the Conifers. 



Tangential section (compare Figs. 7-9). The larger rays appear as 

 minute spindle-shaped bodies that are only exceptionally visible with 

 the lens. They are expanded in the middle of their length to accommodate 

 a horizontal resin-canal which in this species occupies the whole traru- 

 rerse width of the ray (compare Douglas Fir in which this is not the case). 



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