A Polymorphic Trait in Clover (image) Washington University in St. Louis Caption Evolutionary biologist Ken Olsen and Cynthia Vigueira, then a postdoctoral associate in the Olsen lab, examine white clover in the Washington University greenhouse. One morph of this species of clover releases cyanide gas to discourage nibbling. Credit Genevieve Hay Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.