The effectiveness of water repellency isn't just because of the surface chemistry of the material: its texture can work with hydrophobic treatments to create a better effect. On the lotus leaf microscopic cones act to improve repellency. The contact points on the cones is at an increased angle to the leaf's surface, causing water droplets to become more spherical. A duck's feathers provide a similar textured surface for exemplary water repellency. This effect was first explained by Cassie's Law.