APPENDIX II 



THE MICROSCOPIC EXAMmATION OF WOODS 



It is generally recognized that mucli more trustworthy evidence as to the 

 identity of out-of-the-way woods can be obtained hy a microscopic examina- 

 tion than from reports of native opinion or rule-of-thumb tests applied by 

 lumbermen or tmscientij&c traders. Such microscopic examination, it is 

 true, wiU not always enable us to refer an undetermined wood even to its 

 Natural Order, and will in many cases fail to discriminate between the species 

 of one genus ; but, on the other hand, it will often afford, in addition to the 

 evidence of identity, much valuable information as to strength, durability, 

 or other reasons for suitability or unsuitabiHty. 



No one need be deterred from having recourse to this method of examination 

 by any alarm as to its technical difficulties or expense. Though even an 

 examination of a planed surface of wood with a pocket lens may give useful 

 suggestions, a thin transverse section examined under the slightly higher 

 powers of a compound microscope will afford vastly greater information- Any 

 ordinary microscope will suffice, Leitz's dissecting instrument, costing £2 10s., 

 answering admirably ; but it is desirable to have a wide, simple stage and a 

 triple or double nose-piece carrying, preferably, objectives of 1 J in., J in., and 

 J in. focus, though it is seldom that any objective higher than 1 in. is required. 



The preparation of the sections is not difficult. It is quite unnecessary for 

 the ordinary purposes of study to make them of anything like the superficial 

 dimensions of the beautiful preparations of Herr Burkart or Mr. Hough. All 

 that is requisite is to get a transparent section, across the grain, embracing 

 a few annual rings, though it is well to have^ either in one or in more than 

 one section, the pith or structural centre and some of the sapwood as well as 

 the heartwood. Good results can be obtained with weU-seasoned wood; 

 but it is easier to work with green wood, fuM of sap. It should be borne in 

 mind that if a transverse section is not cut precisely at right angles to the 

 vertical axis of the tree the round sections of the vessels will become oval. 

 The end of the specimen having been roughly smoothed with a plane or chisel, 

 a shaving can be easily cut with a well-sharpened plane which, though not 

 equally thin all over, will serve all the purposes of study. The iron of the 

 plane should cut in a radial direction. The wood should, before being cut, 



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