1981 Desert Cactus Plants Mint Block of Four 20 Cent Postage Stamps Scott 1945a By USPS

On December 11, 1981 in Tucson AZ; the USPS issued this se-tenant of four stamps depicting U.S. desert plants. Three of the plants are in the cactus family and one is an agave plant, which most botanists assign the lily or the agave family. Listed are: Agave (Agave deserti) the Saguaro (Cereus giganteus), the Beavertail Cactus (Opuntia basilaris) and the Barrel Cactus (Ferocactus wislizeni). All of the plants are succulent plants as each has fleshy tissues designed to conserve moisture. These stamps were designed by Frank Waslick.