De I. VNER VEW D Forest Trees of the Pacific Slope

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 distinctive
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. No attempt has been
made to translate exactly the technical terms used bv 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 foliage,
fruits, bark, form of trunk and crown. and some other features,
always present. or at least persisting longer than the flowers, are the se
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 possible
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 mav characterize different
individuals of the same species are really within the limits of one
recognized species. They look for absolute uniformity in the characters
of species presented in different individuals, when it reallv 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 according
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 careful
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 details
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.