Leaves Show Looped Networks May Be Better Than Branched: http://www.wired.com/wiredsc...
"“It’s obvious that if you look at leaves, they have a lot of loops,” Katifori says. To find out how the looped networks may be beneficial for the plants, the researchers created a computer model to compare how efficiently different branching patterns could do the job of leaf veins, which move water and nutrients around. “The question we’re asking is, what’s the best network we can build?” Katifori says." - Graham Sergeant