CLASSIFICATION OF CONIFEROUS WOODS 41 



this purpose it is only necessary to take a single shaving, across 

 the grain, with a well-sharpened plane, put it at once into methyl 

 blue or some other die, and then mount it as an ordinary micro- 

 scopic sUde. The first character to be observed is the presence 

 or absence of " pores " or the transverse sections of large trachea. 

 If they are absent, which practically means that the wood is 

 coniferous, we next look for conspicuous resin-canals, and for the 

 presence of heartwood defined by a distinct colour. The out- 

 lines of the annual rings, the hardness, colour, weight, taste and 

 smell of the wood then afford further means of identification ; 

 whilst such microscopic characters as the presence of tracheids 

 in the pith-rays, or of spiral thickening in the tracheids, are only 

 requisite as a last resource. Where, on the other hand, the 

 presence of " pores " indicates that the wood is that of a broad- 

 leaved tree, we first note whether there are, or are not, distinct 

 annual rings, or whether " false rings " of wood-parenchyma are 

 present ; then whether the " pores " are so collected in the 

 inner or spring portion of each ring that we should class the 

 timber in question as " ring-porous " (Fig. 29), or whether they are 

 so scattered that we may call it " diffuse-porous." The grouping 

 of the pores, the prominence of the pith-rays, the weight, hardness, 

 and colour here again furnish subsidiary characters. 



I CONIFEROUS OR KON-POROUS WOODS. 



No visible or conspicuous pores on a transverse section, even 

 when magnified, the wood containing no tracheae or true vessels, 

 except immediately round the pith. Resin-canals often present 

 in the autumn wood. Annual rings generally sharply marked 

 by denser, dark-coloured autumn bands. Pith-rays very fine and 

 numerous, invisible to the naked eye. 



A. Without conspicuous resin-canals. 



1. No distinct heartwood : rings well rounded. 



a. YeUowish-white, soft: no tracheids in the pith-rays. 

 Ihies. The True or Silver Firs, e.g. A. pectindta of 

 Central Europe, A, Webbidna of the Himalayas, A. 

 baUdmea, the Balsam Fir of the North-Eastem United 

 States, and A, grdndis, A. concolor, A, armbilis. A, 

 ndbilis, and A. magnifica of the Western States. 



6. Eeddish, soft, brittle: pith-rays with tracheids. Tsuga. 

 The Hemlock Spruces, including T. canadensis of North- 

 east, and T, Mertensidna of North-west America. 



