In my essay on the origin of flowering plants, I discussed many ideas related to how angiosperms came to dominate terrestrial ecosystems. Representing hundreds of thousands of species and 96% of all terrestrial vegetation, flowering plants are the most successful land plants on Earth. Researchers have long chalked it up to their flowers, which enlist insects and other animals to help them reproduce and spread. But two plant biologists credit the leaves instead. More leaf veins (right) made the plants better photosynthesizers, say Timothy Brodribb, a hydraulic physiologist at the University of Tasmania in Australia, and Taylor Feild, now at the University of Tennessee, Knoxville. “The importance of vein density has never before been so clearly presented,” says Peter Wilf, a paleobotanist at Pennsylvania State University, University Park. Read about their compelling data and argument here.