INTRODUCTORY NOTE 



THE first part of each description contains the information necessary 

 for the identification of each species, except a few which can be known 

 by experience only (i.e. by acquaintance with their external appearance). 



Students are not expected to learn by heart all the details of the first 

 portion but will be expected to observe them, as this course is intended 

 to be a training in observation, for which there is nothing better than 

 a study of the structure of wood. The second portion of each description 

 is intended for use when there is doubt between species. 



The key is for general use and is not necessary as a part of the course, 

 but students are recommended to accustom themselves to the use of 

 such keys. It is frankly empirical, as it is not desirable to introduce a 

 scientific and more difficult key at this stage; moreover all keys are 

 useless as soon as additional species are introduced. 



Be sure of your section by first examining the transverse and com- 

 paring it with the others as, in curly wood sometimes, the former may 

 crop out anywhere. (See specimen 460/6703 of Alder which shows the 

 transverse section on two adjacent edges of the same corner.) 



Always search for the widest and best developed ring. 



Be sure that you are certain which is the inner (pith) side and which 

 the outer (bark) side of the ring. 



In difficult cases, make notes of your observations. 



Wet a portion only of the surface of the wood. 



Be sure that the colour of the wood is not due to external influences 

 (light, weathering, fading, etc.). 



Hold the wood towards the light to observe rays in transverse section 

 and away from the light to see resin-canals on the plank-face. Note 

 colour, hardness, weight, texture, surface, lustre, and smell. 



When comparing two woods, hold them side by side so that a portion 

 of the surface of each is visible under the lens at the same time. 



Never come to a decision before using the lens. 



Acquire the habit of running down the species, step by step, by 

 asking yourself the following questions : 



Is the wood a Conifer or a Broad-leaf ? 



(a) If a Conifer (see p. 35): 



Has it vertical and horizontal resin-canals? 

 Does the horizontal resin-canal occupy much or little of the 

 transverse diameter of the ray in tangential section (see figs. 7-9)? 



