292 



WOOD AND FOREST, 



Of miscroscopic features, the following only have been referred to: 



(8) Tracheids, a description of which is to be found on page 28. 



(9) Pits, simple and bordered, especially the number of simple pits in 

 the cells of the pith rays, which lead into each of the adjoining tracheids. 



For standards of weight, consult table on pages 50 and 192; for stand- 

 ards of hardness, table on page 195. 



Unless otherwise stated the color refers always to the fresh cross-section 

 of a piece of dry wood; sometimes distinct kinds of color, sometimes only 

 shades, and often only general color effects appear. 



HOW TO USE THE KEY. 



Nobody need expect to be able to use successfully any key for the dis- 

 tinction of woods or of any other class of natural objects without some 

 practice. This is especially true with regard to woods, which are apt to 



^ ^ . q 

 "flBfflBI 



far 



Beech 



.Sycamore I .Birch I 



Fig. 130. "Diffuse-porous" Woods, ar, annual ring-; pr, pith raj rs 

 which are "broad" at , "fine" at b, "indistinct" at d. 



vary much, and when the key is based on such meager general data as the 

 present. The best course to adopt is to supply one's self . with a small 

 sample collection of woods, accurately named. Small, polished tablets are 

 of little use for this purpose. The pieces should be large enough, if possible. 

 to include pith and bark, and of sufficient width to permit ready inspection 

 of the cross-section. By examining these with the aid of the key, begin- 

 ning with the better-known woods, one will soon learn to see the features 

 described and to form an idea of the relative standards which the maker 

 of the key had in mind. To aid in this, the accompanying illustrations will 

 be of advantage. When the reader becomes familiar with the key, the work 

 of identifying any given piece will be comparatively easy. The material to 

 be examined must, of course, be suitably prepared. It should be moistened: 

 all cuts should be made with a very sharp knife or razor and be clean and 

 smooth, for a bruised surface reveals but little structure. The most useful 

 cut may be made along one of the edges. Instructive, thin, small sections 

 may be made with a sharp penknife or razor, and when placed on a piece of 



