I picked up this leaf from an American Sycamore tree while walking around our block a couple days ago. The ruler gives an idea of it's size which is too large to be covered by our scanner and measures over 10" from side-o-side. The "veins" show an interesting distribution pattern for reaching every portion of the leaf. Many years ago as the Soil Conservation Service began encouraging the application of conservation practices on a "Watershed basis", it was difficult for people to understand the concept of runoff from many drainage areas converging into given points. Air photos were helpful in visualizing drainage patterns and used to plan dams for flood protection. A leaf like this one pictured could have been used as a "model" since it's "veins" are similar the natural drainage ways in a landscape. There is no limit to the number of instances where this concept is applied in nature as well as in society.