Flora of North America: Volume 7: Magnoliophyta: Salicaceae to Brassicaceae: North of Mexico (Flora of North America North of Mexico)
"A major event in botany."  -The New York Times"Mustards, poplars, and willows are of such major economic significance that anyone interested in economic botany will covet this volume." -- Richard Felger, University Of Arizona Herbarium,Economic Botany