CLASSIFICATION OF CONIFEROUS WOODS 43 



(i) Canals solitary or here and there in pairs ; tracheids 

 without spirals. Heartwood reddish-brown, sapwood 

 yellowish. Knots irregularly distributed. Larches 

 or Tamarack, Ldrix, 

 (ii) Canals in groups or hnes of 8-30 : tracheids with 

 spirals, otherwise resembhng Larch. Douglas Spruce, 

 Fseudotsuga, 

 b. Resin-canals numerous, evenly distributed. Knots in 

 regular whorls. Pinus. 



Pig. 80. — Radial section of Scots Fir (P«^^lS sylvistris). Magnified 100 times. 

 a, narrrow traclieids of autumn wood with small bordered pits on their radial walls ; 

 h, broad spring tracheids ; cd, resin-duct lined with epithelium ; e, parenchyma of 

 pith-ray with large simple pits ; /, tmcheids of pith-ray with small bordered pits and 

 <^entate projections. (From Hartig's Timbers and hoio to knoio th&ni^ by permission of 

 Dr. Somerville and Mr. David Douglas.) 



(i) Wood tolerably hard and firm : transition from spring 

 to autumn wood abrupt : resin-canals more numerous 

 in autumn wood : heartwood reddish : tracheids of 

 pith-ray with dentate projections, when seen in 

 radial section (Fig. 30). Hard Pines. 

 * 1 or 2 simple pits on radial wall of each tracheid of 

 pith-ray. *' Norway pine " of U.S.A., Pinus resinosa, 

 ** 3 to 6 such pits. 



I Wide rings. Loblolly and Short-leaf Pines of 

 U.S.A., P. t(Bda and P. ecMndta ; Northern, 



