JOURNAL OF THE ARNOLD ARBORETUM THE GENERA OF SAPINDALES IN THE SOUTHEASTERN INITEI) STATES ' GEORGE K. BRIZICKY RECENT RESEACH in the fields of floral morphology and anatomy, em-bryology, palynology, comparative anatomy, biochemistry, etc., has madepossible more accurate determination of the systematic positions of manyfamilies and their arrangement into more natural affinity-groups or ordersthan was attainable at the time when the classical Englerian system wasproposed. Since orders usually form the skeleton of every proposed schemefor a "natural system" of the angiosperms, the achievement of the greatestpossible homogeneity seems to be of primary importance. With regard tothis, the splitting of at least some very large and heterogeneous orders ofthe Englerian system (e.g., Geraniales, Sapindales), followed in someinstances by rearrangement of the families among and/or within thesegregated orders, appears to be expedient. Such changes have been carriedout more or less successfully in several recent systems (e.g., Hutchinson,1926 & 1959; Gundersen, 1950; Cronquist. 1957: Takhtajan, 1959). Although the sequence of a number of families of the southeastern UnitedStates which have been surveyed by the author in the Journal of the ArnoldArboretum (vols. 43 & 44, 1962 & 1963) generally corresponds with thatof Engler's system (1936), Takhtajan has been followed primarily in thedelimitation of the orders. Thus, the families Rutaceae, Simaroubaceae,Burseraceae, and Anacardiaceae (as well as Mleliaceae, unpublished) areregarded as members of the order Rutales; the families Sapindaceae, Acer-aceae, and Hippocastanaceae (as well as several others occurring beyond ' Prepared for a generic ilora of the southeastern U nited States, a joint project ofthe Arnold Arboretum and the Gray Herbarium of Harvard I'niversity made possiblethrough the support of George R. Cooley and the National Science Foundation andunder the direction of Carroll E. Wood, Jr., and Reed C. Rollins. This treatment fol-lows the pattern established in the first paper in the series (Jour. Arnold Arb. 39:296-346. 1958) and continued through those in volumes 40-44 (1959 1963). The areacovered is bounded by and includes North Carolina, Tennessee, Arkansas, andLouisiana. The descriptions are based primarily on the plants of this area, with anysupplementary material in brackets. References which the author has not seen aremarked by an asterisk. The author is indebted to Carroll E. Wood, Jr., for his criticism and many valuablesuggestions; to James W. Hardin, for his kindness in reading the manuscript of Hip-pocastanaceae and for his much-appreciated advice; to R. K. Godfrey and J. L.Thomas, respectively, for fresh or preserved materials of Sapindus and lodonaeawhich have been useful in this study; and to Mrs. Gordon W. Dillon, for her carefulhelp in the preparation of the manuscript. The illustration of Exothea was drawn byDorothy H1. Marsh under the supervision of C. E. Wood, Jr.[VOL. XLIV462
BioStor
