AL-SHEHBAZ & SCHUBERT, DIOSCOREACEAE THE DIOSCOREACEAE IN THE SOUTHEASTERN UNITED STATES' IHSAN A. AL-SHEHBAZ AND BERNICE G. SCHUBERT2 DIOSCOREACEAE R. Brown, Prodr. 1: 294. 1810, "Dioscoreae," norn. cons. (YAM FAMILY) Twining [rarely erect] herbs [lianas or subshrubs] with rhizomes or fleshy [rarely woody or corky] tubers, the tubers derived from the hypocotyl, the internode above it, or both; plants with raphides in mucilaginous idioblasts, frequently rich in steroidal sapogenins, and usually accumulating chelidonic acid and lactone alkaloids. Stems smooth, winged [or spiny]; vascular bundles closed, arranged in 2 [or 1] ring(s), the vessels restricted to the roots, stems. and petioles, with scalariform perforation plates; sieve-tube plastids with cu-neate, proteinaceous inclusions. Leaves alternate, rarely opposite or whorled, long petiolate, simple [rarely palmately compound, with 3-7 leaflets], usually cordate, entire, undivided [or palmately lobed], often with embedded muci-laginous pits or nectaries, the tips usually with a distinct pore; venation palmate, with 3-13 converging main veins and anastomosing lateral veinlets; stomata anomocytic, rarely different: trichomes unicellular, eglandular, simple [some-times peglike, furcate (T-shaped), or stellate], often confined to the abaxial surface and along the veins, rarely occurring on the petiole or stem. Inflores-'Prepared for the Generic Flora ofthe Southeastern 'nited States, a long-term project made possible by grants from the National Science Foundation and currently supported by BSR-8415769 ((. E. Wood, Jr., principal investigator), under which this research was done, and BSR-8415637 (N. G. Miller. principal investigator). This account, the 124th in the series, follows the format established in the first paper (Jour. Arnold Arb. 39: 296-346. 1958) and continued to the present. The area covered by the Generic Flora includes North and South Carolina. Georgia, Florida. Tennessee, Alabama. Mississippi, Arkansas, and Louisiana. The descriptions are based primarily on the plants of this area. with information about extraregional members of a family or genus in brackets. The references that we have not verified are marked with asterisks. We are most grateful to Carroll Wood for his support and continuous help during the preparation of this paper, and particularly for his critical review of the manuscript. We should also like to thank Norton Miller for reviewing the paper, Rogers McVaugh for help in leciotypit)'ing DI)oarcua, Charles E. Jarvis for notes and photographs of the type of /). vilt/sa. and Barbara Nimblett for txping the manuscript. We are also grateful to Eli/abeth B. Schmidt and Stephen A. Spongherg for their editorial advice. FIGURE 1,b and k. were drawn by the late Doroth IH. Marsh (DH)M). e and m-o by Ihsan Al-Shehbaz (IAS). and the remainder by Karen Stoutsenherger (KS) under earlier grants. Carroll Wood and Kenneth R. Robertson prepared the material and super ised the illustrations. Preserved ma erial. as well as herbarium specimens in the Arnold Arboretum and the (ras Herbarium, sas used as the basis for the drawings. 'Arnold Arboretum. Harvard University. 22 Divinity Avenue. Cambridge. Massachusetts 02138. �c President and Fellows of Harvard College. 1989.Journal of the Atrnold Arhoretuo 70: 57-95. January, 1989.