Introduction xxi 



Fruit. While varying greatly in type and appearance, fruits 

 are very useful in identification. The different kinds of fruits 

 are pictured and discussed in the text and defined in the glossary. 

 The seeds included in the fruit contain the embryonic plant. 

 To the layman these are generally of secondary utility 

 in identification. 



Twigs. The color, stoutness, central pith, or surface cover- 

 ings and markings may be very useful in identifying trees, 

 especially during the winter months (Fig. 5). As buds, stip- 

 ules, and leaves fall off they leave scars on the twig which are 

 frequently characteristic. Buds are conspicuous on most twigs 

 and helpful in identification. The shape, size, color, number 

 of scales, arrangement, and the presence or absence of terminal 

 bud are important diagnostic characters. 



Bark. The appearance of bark, while varying greatly with 

 age and environment, is often a helpful character in identifi- 

 cation. Color and thickness of the bark, whether it is furrowed, 

 scaly, or smooth, and its taste, are commonly helpful features. 



Wood. The characters of the wood of trees form a separate 

 means of identification which is more technical and difficult 

 than the use of external characters. In this manual only the 

 outstanding wood characters are given, such as the weight, 

 color, and arrangement of large pores (whether ring-porous 

 in a definite ringlike zone, or diffuse-porous and scattered through- 

 out the wood). A statement as to importance and the uses of the 

 woods is also included. 



Silvical characters. The tolerance, sites, associates, reproduc- 

 tion, enemies, roots, life zones, and altitudinal distributions 

 of species are often helpful in identification, and have been 

 included wherever possible. 



In identifying trees it must be remembered that characters 

 are variable and often overlap with those of closely related 

 trees. Wherever possible, identification should not be based 

 on a single character, but on as many as are available. 



