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.