The following chromosome numbers were found in previously uncounted genera of Quillajeae: n = 17 in Lindleya and Kageneckia, and n = 15 in Vatnquelinia. An earlier count of n = 27 in Lyonothamnus is confirmed, but Quillaja, previously reported as n = 17 is shown to have n = 14 in both species currently recognized. This variety of chromosome numbers supports the widely held contention that the tribe is unnatural. Lindleya is regarded here as a member of the Maloideae, where x = 17 is basic, and Vauquelinia is suggested as best placed in this subfamily. The genus Exochorda, known to have n = 8, appears to accord with Prunoideae (x 8), particularly with Oemleria, while Lyonothamnus seems best left in Spiraeoideae (x 9). The peculiarities of the remaining genera, Kageneckia and Quillaja, suggest that they be placed in a separate subfamily. Traditionally the Rosaceae have been treated as comprising six subfamilies, or as in more recent treatments four, with the Neuradoideae and Chrysobalanoideae recognized as distinct families. The remaining subfamilies, Spiraeoideae, Prunoideae, Maloideae and Rosoideae, are by and large natural groupings and, as might be expected from so ancient and comparatively primitive dicot group, relatively distinct from one another. This classical treatment of the family is supported by chromosomal data. The basic chromosome number in the family appears almost certainly x = 9 (Raven, 1975) and this base number is found in the Spiraeoideae (with several notable exceptions) usually regarded as the least specialized of the four subfamilies with its partly to completely free carpels and dry, usually follicular fruits. In the subfamily Prunoideae the base number is x = 8, in the Maloideae, x = 17 (clearly a palaeotetraploid group), and while a base number of x = 7 predominates in the Rosoideae, x = 9 and x = 8 also occur in several lines. The Spiraeoideae appear to be the least homogeneous of the rosaceous subfamilies, the discordant elements being a number of genera usually placed in the tribe Quillajeae, which have in common dry, dehiscent fruits with winged seeds. In its broadest sense (Hutchinson, 1964) the tribe comprises the following genera: Quillaja, Kageneckia, Vauquelinia, Lindleya, Exochorda, and Lyonothamnus. The last-mentioned is included only by Hutchinson and differs in having two to three carpels in contrast to five in the other genera, and, in spite of statements to the contrary, its seeds are not winged. Various authors since Spach 'I would like to thank Peter H. Raven, Director of the Missouri Botanical Garden, for his encouragement in this project and assistance in obtaining material for study, and W. G. D'Arcy, also of the Missouri Botanical Garden for his helpful comments. Thanks are also extended to the following for their cooperation and help in obtaining the seed or cytological material used in this study: Jerzy Rzedowski, Escuela de Ciencias Biologicas, Mexico City, Mexico; Marshall C. Johnston, University of Texas, Austin, Texas; Charles T. Mason, University of Arizona, Tucson, Arizona; Bruce Bartholomew, Berkeley Botanical Garden, Berkeley, California; Barbara Lilley, University of California, Stanford, California; Ramon Ferreyra, Herbario San Marcos, Lima, Peru. 2 B. A. Krukoff Curator of African Botany, Missouri Botanical Garden, 2315 Tower Grove Avenue, St. Louis, Missouri 63110. ANN. MissouRi BOT. CARD. 63: 200-206. 1976. This content downloaded from 157.55.39.45 on Fri, 02 Sep 2016 06:09:39 UTC All use subject to http://about.jstor.org/terms 1976] GOLDBLATT-CYTOTAXONOMY OF THE QUILLAJEAE 201 (1834: 429), who excluded the Quillajeae from the Spiraeoideae, have implied or stated that the tribe is not a natural alliance. Schulze-Mentz (1964), for example, admits only Quillaja, Kageneckia and Vauquelinia, while placing Exochorda and Lindleya in the Exochordeae and Lyonothamnus in the Sorbarieae. Certainly, differences between some genera of the Quillajeae seem greater than between other tribes and even subfamilies of the Rosaceae. This is reflected in what little has been known of the cytology of the group with reported chromosome numbers in three genera ranging from n = 27 (x = 9?) in Lyonothamnus, n = 7 in Quillaja, and n = 8 in Exochorda (Table 1), the latter genus already associated with the Prunoideae because of its cytology (Raven, 1975). Thus cytological data amplifies the likelihood that the alliance is unnatural. The present study was undertaken in the hope that a more comprehensive knowledge of the cytology of the tribe will lead to a better understanding of the affinities of the genera placed in the Quillajeae and of the overall evolution in the Rosaceae.