10 INTRODUCTION. 



terms. It is believed that the chief distinguishing characters of trees 

 may be readily observed by laymen if clearly pointed out in ordinary 

 language. The color of wood given refers to heartwood: sapwood is 

 described only when it is materially different from the usual whitish 

 color of such wood. 



The illustrations are relied upon chiefly to define the important dis- 

 tinctive characters. Additional characters, difficult or impossible to 

 show in drawings, such as the roughness, very minute hairiness, etc., 

 of foliage or other parts, are briefly described. Xo attempt has been 

 made to translate exactly the technical terms used by botanists to 

 describe, for example, the different types of hair, wool, and other 

 appendages which often mark the leaves and twigs of trees. Little 

 attention has been given to defining or illustrating such transient 

 characters as flowers and young or immature foliage. Mature foli- 

 age, fruits, bark, form of trunk and crown, and some other features, 

 always present, or at least persisting longer than the flowers, are those 

 most readily observed, and for this reason have been singled out and 

 emphasized. Some trees are very easily identified by the special 

 shape of their leaves, the color and character of their bark, or the 

 form of their crown, whereas the recognition of others requires all 

 available evidence. It must be borne in mind also that some trees, 

 especially conifers, have very dissimilar leaves, buds, and bark on 

 different parts of the crown and trunk. 



A long experience has taught the author that it is difficult for lay 

 students of trees to appreciate the variation in shape and size possi- 

 ble in the leaves and fruits, and in the bark characters of a single 

 species. It is hard for them to understand that such minor differences 

 in the size and form of leaves and fruits as may characterize different 

 individuals of the same species are really within the limits of one 

 recognized species. They look for absolute uniformity in the char- 

 acters of species presented in different individuals, when it really is 

 not to be found. The student will, therefore, often find it exceedingly 

 difficult to identify some forms of a species. Representative leaves, 

 fruits, and other characters have been illustrated and described ac- 

 cording to the best judgment of the author, who has tried to give the 

 best of the knowledge he applies in making an identification. The 

 student may find tree forms slightly or considerably different in 

 details from those illustrated and described here, and will be in 

 doubt. He will be able to settle doubtful points only by much care- 

 ful field study and the observation of all that can be found distinctive 

 in trees. In order to know even a few trees well, a multitude of de- 

 tails must be learned and remembered, especially if the species are 

 closely related. Much of the dendrologist's knowledge of trees is 

 gained through long study by a partly unconscious absorption of 

 small, indescribable, but really appreciable, details. 



