Constructal News Evolution is not random admin - February 1, 2015 0 The tree is the natural flow design that evolves to achieve flow access between one point and a volume. Alternating trees achieve flow access between two planes. Natural porous media such as soil exhibit multi-scale flow structures consistent with the multiple scales and performance of alternating trees. An intimate discussion with Prof. Adrian Bejan, about Design in Nature and the Constructal Law, beautifuly illustrated with pictures, hand drawings, and videos. KOGAINON.com, Knowledge Keepers: Design in Nature, Meeting Professor Adrian Bejan at Duke University.