JOURNAL OF THE ARNOLD ARBORETUM THE GENERA OF ROSACEAE IN THE SOUTHEASTERN UNITED STATES * KENNETH R. ROBERTSON Subfam. ROSOIDEAE About 520 species (excluding the apomictic complexes of Alchemilla,Potentilla, and Rubus) in 41 genera and eight tribes. Eleven genera repre-senting seven tribes occur in the southeastern United States. Two, Alche-milla and Duchesnea, are introduced. Kerria and Rhodotypos may possiblybe established locally in our area and are included in the key to genera (seediscussion under Neviusia). Two genera, Dalibarda and Neviusia, are re-stricted to eastern North America, eleven to western North America, sevento Eurasia, four to Africa and Macaronesia, and three to South America.Twelve genera are largely of the North Temperate region; Acaena is cir-cum-Antarctic. Tribe Adenostomateae includes a single genus with twospecies, Adenostoma fasciculatum Hooker & Am., 2n 18, and A.sparsifolium Torrey, 2n = 18, both from the Upper Sonoran Zone ofCalifornia and Baja California (see Anderson, subfamily references, for astudy of introgression in A. fasciculatum). Base chromosome numbers in the tribes of Rosoideae are nine in theKerrieae (Neviusia has counts of 2n = 14, 16, 18); seven in the Ulmarieae(some aneuploidy); seven in the Rubeae; seven in the Fragarieae; seven inGeum, Waldsteinia, and Coluria and nine in the other genera of Dryadeae;eight in Alchemilla and seven in the remaining genera of Sanguisorbeaethat have been examined cytologically; nine in the Adenostomateae; andseven in the Roseae.SUBFAMILY REFERENCES:ANDERSON, E. Introgression in Adenostoma. Ann. Missouri Bot. Gard. 41: 339-350. 1954.BESSEY, E. A. The comparative morphology of the pistils of the Ranunculaceae, Alismaceae and Rosaceae. Bot. Gaz. 26: 297-313. pl. 25. 1898.BRESINSKY, A. Bau, Entwicklungsgeschichte und Inhaltsstoffe der Elaisomen. Studien zur myrmekochoren Verbreitung von Samen und Friichten. Bibliot. Bot. 126: 1-54. 1963.CHOAY, E. Recherches anatomiques et physiologiques sur les Dryadies. 128 pp. 4 pls. Paris. 1888.*JACKSON, G. The morphology of the flowers of Rosa and certain closely related genera. Am. Jour. Bot. 21: 453-466. 1934. [Dalibarda, Dryas, Geum Rubus, and H'aldsteinia.] * Continued from volume 55, p. 332.[VOL. 55
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