6 PREFACE 
Scientific names are marked so as to indicate the pronuncia- 
tion. The vowel of the accented syllable is marked by the grave 
accent (') if long, and by the acute (’) if short. 
In the preparation of this book the author has received much 
valuable aid. His thanks are especially due to the authorities 
of the Arnold Arboretum, Boston, Massachusetts, and of the 
Missouri Botanical Garden, St. Louis, for information in regard 
to the hardiness of species; to Mr. John H. Redfield, of the 
Botanical Department of the Philadelphia Academy of Nat- 
ural Sciences, for books, specimens from which to make illus- 
trations, etc.; and to Dr. A. C. Stokes, of Trenton, New Jersey, 
for assistance in many ways, but especially for the accurate 
manner in which he has inked the illustrations from the au- 
thor’s pencil-drawings. 
The author also wishes to acknowledge the help received 
from many nurserymen ‘in gathering specimens for illustra- 
tion and in giving information of great value. Among these, 
special thanks are due to Mr. Samuel C. Moon, of Morrisville 
Nurseries, who placed his large collection of living specimens 
at the author’s disposal, and in many other ways gave him 
much intelligent aid. 
