CHROMOSOME NUMBERS OF TROPICAL AMERICAN GRASSES (GRAMINEAE): 51,2 GERRIT DAVIDSE3 AND RICHARD W. POIL4 ABSTRACT Chromosome numbers and meiotic behavior are reported in 101 collections of grassesrepresenting 42 genera and 85 species. First chromosome reports are given for the following21 species: Agrostis turrialbae, n = 14; Andropogon hypogynous, n = 30; Axonopus pruinosus,n = 30; Aristida riparia, n = 11; A. setifolia, n = 11; A. torta, n = 11; A. venesuelae, n = 22;Chusquea scabra, n = 20; Festuca chiriquensis, n = 14; Gymnopogon spicatus, n = 10;Muhlenbergia lehmanniana, n = 10 + 2B; Olyra lateralis, n = 18; Panicum guianense,n = 20; P. macranthum, n = 27; P. olyroides, n = 18; P. pyrularium, n = 18; Paspalumgardnerianum, n = ca. 20; Pereilema brasilianum, n -20; Stipa hans-meyeri, n = 11; Swal-lenochloa longiligulata, n = 20; Swallenochloa weberbaueri, n = 20. Counts differing frompreviously reported numbers are given for the following 5 species: Axonopus fissifolius, n = 30;Pappophorum pappiferum, n = 50; Paspalumn carinatum, n -10; P. minus, n = 25; Pennisetumsetosum, n = 18. This paper is a continuation of our earlier studies on the chromosome num-bers of tropical American grasses (Pohl & Davidse, 1971; Davidse & Pohl, 1972a,1972b, 1974). Tropical America continues to be one of the most poorly studiedareas in the world in terms of known chromosome numbers of grasses. We in-tend to continue to provide basic information concerning chromosome numbersand meiotic behavior of tropical American grasses as this becomes available. Since our review of important contributions dealing with chromosome num-bers of tropical American grasses (Davidse & Pohl, 1974), several other papershave been published: Moraes Fernandes et al. (1974), Koch (1974), Hickenbicket al. (1975), and Quarin (1977). All chromosome counts were made from squashes of microsporocytes. Themethods used are those noted in Davidse & Pohl (1972a). Vouchers for thePohl and the Pinette specimens are deposited in the Iowa State UniversityHerbarium (ISC), and for the Davidse specimens in the Missouri Botanical Gar-den Herbarium (MO). Voucher slides are available for most of the counts atMO. RESULTS AND DISCUSSION A complete list of the species studied, their chromosome numbers, and thevoucher specimens is given in Table 1. Two asterisks (**) after a number indi-SJournal Paper No. J-9033 of the Iowa Agriculture and Home Economics ExperimentStation, Ames, Project 1833. * Part of the field work was supported by N.F.S. grants DEB 73-00834 A01 to Davidse andGB-32085 to Pohl. We would like to thank Dr. Enrique Forero, Bogota for his assistance withthe Colombian field work, and Dr. Tobias Lasser, Dr. Julian A. Steyermark, Dr. Stephen S.Tillett, and Mr. Gilberto Morillo, all of Caracas, for assistance with the Venezuelan field work. SMissouri Botanical Garden, 2345 Tower Grove Avenue, St. Louis, Missouri 63110. SDepartment of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50011.ANN. MIssourI BOT. GARD. 65: 637-649. 1978. 0026-6493/78/0637-0649/$01.45/0
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