Alfred Rehder was the curator of the Herbarium of the Arnold Arboretum. He was German-born and a self-taught taxonomist, arriving at the Arboretum in 1898 and first employed to weed the shrub collection. His keen taxonomic judgment was quickly recognized, however. The Manual of Cultivated Trees and Shrubs Hardy in North America Exclusive of the Subtropical and Warmer Temperate Regions, best known as "Rehder's Manual," was first published in 1927. Here we have reprinted the second edition, published in 1940.