Figure 2. Water transport pathway in outer pine cones.

(a) Schematic diagram of a pine cone indicate the route of water transport. ① The droplet reaches the center of the pine cones ② Water is absorbed by the bract scales and spreads into the scales and fibers. ③-1 Most water is transported to the inner scales. ③-2 A small amount of water spreads to the fibers ④ The water in scales eventually causes the structural transformation. The figure was created by the authors using 3ds Max software (Autodesk Inc., USA). (b-g) Water droplet moves toward the center of the pine cones along the slopes of the scales and absorbed through bract scales. The blue arrows indicate the trajectories of water droplet, where the lengths of each arrow represent moving distance of the droplet. Scale bar, 4 mm.