CHROMOSOME COUNTS AND TAXONOMIC NOTES FOR COMPOSITAE FROM THE UNITED STATES AND MEXICO

Chromosome counts are reported for 167 taxa representing 160 species and 76 genera of Compositae. First reports for 27 species and 2 infraspecific taxa are included. New chromosome numbers are reported for 9 additional taxa. The genus Carminatia DC. is merged with Brickellia Ell. resulting in two new combinations: Brickellia tenuiflora (DC.) Keil & Pinkava and Brickellia recondita (McVaugh) Keil & Pinkava. CHROMOSOME COUNTS serve as a reservoir of data for biologists concerned with systematic and evolutionary investigations. Unlike the morphological information content of specimens, which can be measured and remeasured by succeeding generations of botanists, chromosomal information is ephemeral and is not directly retrievable from a dried specimen. Consequently, documentation of chromosome numbers and meiotic irregularities serves as a unique source of information for both current and future investigators. In this publication, we are presenting 270 chromosome counts representing 76 genera, 160 species, and 7 additional infraspecific taxa from the Compositae (Table 1). Counts are published here for the first time for 27 species and for 2 infraspecific taxa and previously unpublished chromosome numbers are reported for 9 additional taxa. Both Table 1 and the accompanying discussion are arranged according to a modification of the tribal system of Hoffmann (1894). Discussion is provided only where it is necessary to add to or clarify material presented in the table. METHODS-Immature capitula were killed and fixed in the field in modified Carnoy's fixative (4 [or 6] chloroform: 3 ethanol: 1 glacial acetic acid; v:v). In a modification of the methods of Beeks (1955), floret buds were stained with ironacetocarmine and were squashed in a drop of Hoyer's solution. All chromosome counts were determined from meiotic microsporocytes and were documented with camera lucida drawings. OBSERVATIONS AND DISCUSSION-EUPATORIEAE-Barroetea is very closely related to Brickellia (Robinson, 1917). Both genera have the 1 Received for publication 22 January 1975. We acknowledge the cooperation of the curators of the following herbaria for making specimens available for our studies: ASU, GA, GH, MICH. We thank those collectors who contributed plant materials in support of our research. same base number (x = 9) and are very similar in habit. Barroetea apparently differs from Brickellia only in having setiferous teeth on the leaves and flattened rather than terete achenes. Further investigations may result in the merger of the two genera. Our first report of n = 9 for the plant long known as Carminatia tenuiflora DC. prompted a re-evaluation of the genus Carminatia. Carminatia is morphologically very similar to Brickellia (x = 9) in many respects but differs in having 5angled rather than 10-angled achenes and plumose rather than merely scabrous pappus bristles (Robinson, 1917). Flyr (1968) stated that the number of angles on the achene is not a consistent character for distinguishing Brickellia from its close relatives, and Shinners and McVaugh (1968), in arguing for the merger of Kuhnia and Brickellia, indicated that a pappus of plumose bristles is not a satisfact-ory generic character either. The presence or absence of hairs on the style bases, a character used by King and Robinson (1972) to separate Brickellia from Carminatia in Nueva Galicia, is not consistent since several species of Brickellia (e.g., B. scoparia (DC.) A. Gray, B. spinosa A. Gray) have glabrous styles bases. We have concluded that there is no justification for maintaining Carminatia as a genus distinct from Brickellia. We therefore propose the following new combinations: Brickellia tenuiflora (DC.) Keil & Pinkava, comb. nov. Carminatia tenuiflora DC. Prodr. 7: 267. 1838. Brickellia recondita (McVaugh) Keil & Pinkava, comb. nov. Carminatia recondita McVaugh, Contr. Univ. Mich. Herb. 9(4): 384. 1972. ASTEREAE-Aster is cytologically one of the most complex genera of the Astereae. Chromosomal evolution has apparently involved both aneuploidy and polyploidy, with polyploid series arising from several base numbers. Our new re-