Synopsis: Soybean leaf hairs slowed wind by 40% at a distance of 0.50 mm. from the leaf surface. When the hairs were liquid‐filled they contributed slightly to the cuticular transpiration of the leaf, but when the hairs were empty they decreased transpiration by 20%. The water permeability of the hair surface was 3 ✕ 10−7 cm sec.−1 bar−1.