Research Summary: Leaf water loss was compared under different air movement conditions. Data summary: the boundary layer was 4.0 mm thick with still air and water loss 1.2 g/hour, 1.5 mm with a gentle fan and 3.4 g/hour, and 0.7 mm with a strong fan and 5.1 g/hour. The term "boundary layer" means the thin layer of air next to a surface. How should the term "boundary layer" be understood from the reported measurements?