INTRODUCTORY STATEMENT 



works for complete scientific descriptions of the 

 plants discussed: Gray's Manual of Botany of the 

 Northern United States (east of the Rockies) ; Brit- 

 ton and Brown's Illustrated Flora of the United 

 States and Canada (the same territory as covered by 

 Gray) ; Small's Flora of the Southeastern United 

 States; Watson's Botany of the Geological Survey of 

 California; Coulter's New Manual of Botany of the 

 Central Rocky Mountains; Wootton and Standley's 

 Flora of New Mexico. 



