Dr. Melvin Tyree is awarded the nineteenth Marcus Wallenberg Prize for his pioneering scientific discoveries leading to basic understanding of water transport in trees. His path breaking research has elucidated the hydraulic architecture of a wide range of temperate and tropical trees. Dr. Tyree’s scientific work has been fundamental to the understanding of stress induced malfunction of water transport in trees. His theoretical contribution as well as the development of methods has contributed to the understanding of the importance of cavitation in ecology and physiology of trees. Tyree’s work gives us perspective on the evolution of wood structure and on the distribution of trees in forests around the world.