viii INTRODUCTION 



no key in itself is to be regarded as final, and determinations 

 should be checked up by reference to Bailey's Standard Cyclo- 

 pedia of Horticulture, in which are to be found full descrip- 

 tions and references to excellent illustrations. To facilitate 

 this use, technical considerations are waived and the names 

 here used for genera and species are conformed to the Cyclo- 

 pedia: but where native genera are differently named in cur- 

 rently used Manualsi, these names are added as synonyms. 



The keys do not bring together the names of genera that 

 are related; but their division into sections dealing respec- 

 tively with Trees, Shrubs, Undershrubs and Cover plants, and 

 Climbers, gives them a certain comparative value in addition 

 to convenience of reference; and this is increased by the 

 grouping in various places of evergreen and deciduous, armed 

 and spineless forms, etc., and by a division of the undershrubs 

 according to their habit of growth. 



The relationships of the genera and the relative land- 

 scape or other importance of families are to be seen at a glance 

 when reference is made to the systematic part of the book. An 

 innovation that it is hoped may prove useful, and that affords 

 suggestions for further observation on dependable though rare- 

 ly used characters, is to be found in the brief descriptions of 

 the genera, in which more space is given to wood, bud, leaf- 

 scar, foliage and inflorescence than to the more transient de- 

 tails of flower and fruit on which botanical classification 

 largely rests. 



Though the manuscript has been subjected to critical use 

 by individuals and classes, it is probable that errors have been 

 overlooked, or introduced in the effort to make betterments. 

 For these, apologies arc tendered; but the hope is entertained 

 that its shortcomings may be outweighed by a general useful- 

 ness of the little handbook, which is intended to meet a need 

 that my own experience as a teacher shows to be very real now 

 that plant materials are so much studied and used. 

 Urbana, Illinois, June 30, 1917. 



