Introduction 



HOW TO USE THE KEYS. 



Since all the genera, e. g., elm, oak, willow, pine, etc., and nearly- 

 all the species, e. g., red elm, cork elm, red oak, white oak, bur oak, 

 etc., are illustrated, it will often be possible to find the name of a 

 tiee or shrub by turning directly to the illustration. This is especially 

 true when the plant is known to belong or thought to belong to a 

 particular family or genus. For the beginner, however, this method 

 would usually prove long and tedious, as well as uncertain in its re- 

 sults. Much the better method is to make use of the two keys found 

 on pages n and 16. The first key is based chiefly upon the leaves 

 and twigs, and is for use from the time the leaves unfold until they 

 drop in the fall. The second key is based primarily upon the structure 

 of the flower, and hence can be used only with flowering specimens. 

 It is especially helpful in the spring for the large number of deciduous 

 trees in which the flowers appear before the leaves, as well as for 

 many woody plants in which the leaf characters are similar. While 

 it is possible to determine the names of trees and shrubs in their winter 

 condition, it is so difficult for anyone who does not already possess 

 considerable knowledge of them, that such a key has been omitted. 

 The best plan for the beginner to follow is to become acquainted 

 with individual trees and shrubs during the summer, and then learn 

 the habits and appearance of these same individuals during the winter. 



Both keys are made after the same plan, namely, of making a 

 choice for the most part between two alternatives. For example, if 

 one wishes to find the name of the common upland oak by means of 

 a leaf twig, he would turn to the "Key to the Genera" on page 11. 

 Here the first choice must be made between "I. Leaves needle-like or 

 scale-like", and "II. Leaves not needle-like or scale-like." The former 

 are the leaves of pines, spruces and tamaracks, the latter of the broad- 

 leaved woody plants, such as elms, oaks, willows, lilacs, etc. Under 

 "11", the oak clearly belongs in "1. Trees", and not in "2. Shrubs or 

 vines" (page 13). Again, under "1", choice must be made between 



