It???s called the endosperm, and it is what pops in popcorn (left) and forms the bulk of what is in flour, rice, oats, and other grains, providing humans with two out of every three calories worldwide. ???You take endosperm off the table, and you have fern fiddleheads and not much more [to eat],??? says William Ned Friedman, a botanist at the University of Colorado, Boulder. ???Even a grain-fed co