When you think of citrus fruits, what comes to mind? For most North Americans, oranges, mandarins, tangerines, grapefruits, lemons, and limes are standard fare. Some adventurous citrus eaters also include pomelos, kumquats, tangelos, blood oranges, and clementines. You might be surprised to learn that there are over 100 different varieties of citrus fruits. Evidence suggests that all of these varieties are hybrids of ancient species, including citron, mandarin, pomelo, and kumquat.