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Summary Cytogenetic analysis on two lots of maize genotypes consisting of inbred lines, singlecross hybrids and double-cross hybrids grown in the South and Center West Regions of Brazil revealed the occurrence of spontaneous mixoploidy in the anthers of some plants. In the South Region the anthers showed only diploid and tetraploid cells, with the tetraploid ones presenting nuclear fusion. In the genotypes grown in the Center West Region the anthers showed a mixture of diploid, tetraploid, hexaploid and octaploid cells. In addition to nuclear fusion, some cells of these genotypes presented just cytoplasm fusion, with the nuclei remaining individualized. The percentage of polyploid cells ranged from 1.0 to 47.6. The probable origin of the phenomenon and its implications in maize breeding are discussed.

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Summary Somatic chromosome numbers were determined in 10 populations of Pfaffia glomerata, also known as "Brazilian ginseng", collected from different regions of Brazil and Argentina. Nine populations showed 2nϭ34 and one 2nϭ32, 33. Although chromosomes were very small, a pair of satellited chromosomes per karyotype was reported in almost all the populations. Chromosomes were predominantly metacentric and submetacentric. Meristematic interphase nuclei showed areticulate chromatin structure. Prophase chromosomes had deeply stained proximal blocks of condensed chromatin. This is the first cytological report including chromosome counting for the genus Pfaffia, a genus of the Amaranthaceae family with several species of economic importance due to their high content of ecdysteroid glycosides. The latter is a substance similar to that found in the genus Panax, "the Korean ginseng", widely used as medicine.