Summary: Paspalum pumilum Nees had a chromosome number of 2n = 20. The chromosome number in P. arechavaletae Hack., P. cromyorhizon Trin. ex Doell., P. exaltatum F. & C. Presl, P. guenoarum Arech., and P. lividum Trin. ex Schlecht. was 2n = 40; and in P. mandiocanum Trin. it was 2n = 60. Meiosis was regular in P. pumilum, P. arechavaletae, P. exaltatum, and P. mandiocanum with primarily bivalent pairing. P. cromyorhizon and P. guenoarum had frequent quadrivalents, and meiosis in P. lividum was the most irregular with lagging chromosomes and micronuclei. A study of megasporogenesis and embryo sac development in each species showed that P. pumilum and P. arechavaletae were sexual and the other five species reproduced by apomixis. The type of apomixis was apospory and, with the exception of P. mandiocanum, species were pseudogamous.