Notes on Psychotria Subgenus Heteropsychotria (Rubiaceae: Psychotrieae) in Mexico and Northern Central America Charlotte M. Taylor Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. David H. LorenceNational Tropical Botanical Garden, P.O. Box 340, Lawai, Kauai, Hawaii 96765, U.S.A.ABSTRACT. Expanded descriptions, comments ongeographic ranges and infraspecific variation, andcomplete synonymy are presented for Psychotriaminarum, P. galeottiana, and P. phanaerandra(Standley & Steyerm.) Lorence, a new combinationmade here that is based on Palicourea phanaeran-dra Standley & Steyerm. The new species Psycho-tria juarezana C. M. Taylor & Lorence from south-ern Mexico is also described. Psychotria I. is a pantropical genus of about1,500 species of herbs, shrubs, and small trees. Itis represented by three subgenera in the Neotropics.All subtropical species are assignable to subgenusPsychotria or subgenus Ileteropsychotria Stey-erm., except P. microdon (DC.) Urban. This specieswas included in subgenus Psychotria by Steyermark(1974) and other authors, but is better placed insubgenus 7Ttramerae (Hiern) E. Petit (Iamilton,1989). Subgenus Tetramerae comprises speciesfound in the Palaeotropics, plus this one. It is char-acterized by leaves that dry pale green, pyrenes withthe abaxial ("dorsal") surface smooth except for amedian keel, persisting marcescent stipules, and lat-eral branches in opposite pairs (Hamilton, 1989;Verdcourt, 1976). In contrast, subgenus lleteropsy-chotria is characterized by leaves that dry darkgreen to brown or gray, pyrenes with three or moreribs on the abaxial surface, stipules that may bepersistent or deciduous but are not marcescent, andlateral branches that are usually not opposite. Psy-chotria microdon is found in the Antilles and ad-jacent continental lowlands, and probably representsan example of long-distance dispersal. Members ofsubgenus Tetramerae characteristically have bac-terial nodules in their leaves (Verdcourt, 1976), afeature not found in the neotropical members ofPsychotria (including P. microdon). The two other subgenera found in the Neotropicsencompass at least 500 species. These have beenstudied in the framework of regional floras but havenot been treated comprehensively. The species ofsubgenus Psychotria have recently been treated in-depth for Mexico and Central America (IHamilton,1989). This is the area of highest diversity for thissubgenus, with about 60 species. Subgenus Ileter-opsychotria includes approximately twice as manyspecies in this same area, and many more in SouthAmerica. Cephaelis Sw. was studied by Steyermark (1972),who concluded that it comprised an assemblage ofspecies that in many cases were more closely relatedto various members of Psychotria than to othermembers of Cephaelis. He therefore combined (e-phaelis with Psychotria subg. Hleteropsychotria,making the appropriate combinations for the florasof the Guayana Highlands (Steyermark, 1972) andVenezuela (Steyermark, 1974). Combinations re-main to be made for many species that are not foundin Venezuela (e.g., Taylor et al., 1991). A modern infrageneric classification of Psycho-tria subg. Heteropsychotria (including Cephcelis)was also begun by Steyermark in his South Americanstudies (1972), but was not extended to the Meso-american species. Unfortunately, Steyermark's sys-tem did not include explicit diagnoses of his groups,but was intended instead "to show apparent rela-tionships between the taxa presented." The flora ofnorthern Mesoamerica includes many of the speciesSteyermark classified, as well as endemic relativesof these species, so his classification can be extendedin general to the region. However, the flora of north-ern Mesoamerica is not simply a northward exten-sion of the South American flora, but does have itsown identity as a phytogeographic province (Takh-tajan, 1986); the existing infrageneric classificationfor subgenus Heteropsychotria is inadequate to al-low us to classify the species treated here. We present here expanded descriptions, com-ments on geographic range and infraspecific vari-NovoN 2: 259-266. 1992.