plest and most frequently used are fresh weight and dry weight. The procedures presented here are modified from an exercise in Dodds and Roberts (1985). These procedures were used to determine growth curves of sweet potato (Ipomoea batatas) root explants grown on Murashige and Skoog medium. Sweet potatoes are commonly sold as 'yams' in your local grocery store; however, sweet potatoes are dicots and the true yams are monocots belonging to the genus Dioscorea. We have found that sweet potatoes are useful tools for this demonstration. The roots provide large amounts of sterile tissue that respond well to the culture conditions used.