viii Introduction 



and leaf-scars, particularly those of ordinary branches rather 

 than suckers or spurs, before beginning to use the key. When 

 this practice is followed, after a few familiar species have 

 been traced through so as to give facility, the key will be 

 found simple, direct and conclusive in nearly every case; and 

 native and introduced species, as well as genera, may be 

 named for the most part. 



The present volume, though conifers are excluded, deals 

 with 326 genera belonging to 93 families. Species and espe- 

 cially varieties are not differentiated to the same extent as in 

 the earlier volume, but the keys lead to the names of about 

 1100 such forms. 



As in the earlier volume, questions of nomenclature have 

 been waived, and the same names are used in both books 

 except for correction of a few oversights in the first, so that 

 reference may be made readily to the Standard Cyclopedia for 

 other information concerning the' plants; and this is even 

 more necessary than when names are learned from summer 

 characters. 



