JOURNAL OF THEARNOLD ARBORETUMVOL. 51 JULY 1970 NUMBER 3 THE GENERA OF ACANTHACEAE IN THE SOUTHEASTERN UNITED STATES 1 ROBERT W. LONGACANTHACEAE A. L. de Jussieu, Gen. P1. 102. 1789, "Acanthi," nom. cons. (ACANTHUS FAMILY) Herbs [shrubs] or vines [rarely small trees]. Leaves simple, oppositeexstipulate; pubescence of stems and leaves of simple hairs; cystolithsof various forms often present in parenchyma or epidermis. Inflorescencesbasically cymose (dichasial), often condensed in leaf-axils, modified intoracemes or panicles, or flowers sometimes solitary. Flowers perfect, nearlyactinomorphic to zygomorphic; bracts and bracteoles usually present andoften colored, sometimes large and enclosing the flower. Calyx segments5, occasionally 4, not infrequently fused, persistent. Corolla sympetalous,the limb 5-lobed or bilabiate, rarely 1-lipped, lobes convolute or im-bricate in bud. Nectariferous disk nearly always present, below ovary. 1Prepared for a generic flora of the southeastern United States, a project of theArnold Arboretum and the Gray Herbarium of Harvard University made possiblethrough the support of the National Science Foundation (Grant GB-6459X, principalinvestigator Carroll E. Wood, Jr.). The treatment in this paper, which is the 52ndpublished in the series, follows the format established in the first paper (Jour.Arnold Arb. 39: 296-346. 1958). The area covered includes North and South Caro-lina, Georgia, Florida, Tennessee, Alabama, Mississippi, Arkansas, and Louisiana.The descriptions are based primarily on the plants of this area, with additional in-formation in brackets. References which have not been seen and verified aremarked by an asterisk. The manuscript for this paper was prepared while I held a Mercer Research Fel-lowship at the Arnold Arboretum in the latter half of 1968. I want to express mythanks for the facilities extended to me during my stay in Cambridge and to theseveral people who have aided substantially with this treatment of the Acanthaceae.Dr. Carroll Wood has spent a great deal of time in editing and checking the manu-script, in making numerous additions and suggestions, in preparing the dissectionsfor and supervising the illustrations, and in preparing the legends for them. Theillustrations are the work of the late Dorothy H. Marsh (FIGURE 5, i-n) and ofDiane C. Johnson and Virginia Savage, whose initials will be found on the appro-priate ones. Mrs. Mary C. Dillon carefully checked most of the references and theabbreviations of books and journals, and Mrs. Nancy Dunkly verified most of theremainder and prepared the typescript. My appreciation is extended to them all.