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Among a natural population of Coix aquatica Roxb., a pentasomic (2n + 3; 2n = 15) was isolated and studied cytologically for the first time. The extra homologous chromosomes in the plant behaved normally, as they did not disturb the rest of the bivalents through meiosis except for the stickiness and rare occurrence of a few univalents and chromosome fragments. The majority of pollen mother cells (PMCs) showed five bivalents and a pentavalent at diakinesis. The different anaphase segregations led to the formation of hypo- and hyper-ploid male gametes from n-1 (n = 5) to n + 4 (n = 10) chromosomal constitutions. Although the chromosomal configurations towards the later stages were found to be sticky in most of the meiocytes, the meiosis was clean, giving rise to pollens that appeared to be normal. The plant yielded a few fertile seeds also. The origin of this higher polysomic is considered to be through the fusion of male and female super haploid gametes produced by the trisomics that arose from the 2n = 12 Coix taxon.

A series of aneuploids, starting from nullisomy (2n-2 i. e. 2n=18) to hexasomy (2n+4 i. e, 2n=24), has been isolated from a natural wild population of Coix gigantea Koen ex Roxb., a member of the tribe Maydeae of Poaceae. Among a total of 96 aneuploids isolated, the various chromosomal variants appeared as: 68 nullisomics, 13 monosomics, 12 trisomics and one each a tetrasomic, a pentasomic and a hexasomic. Higher polysomics-the pentasomic and the hexasomic-are reported for the first time in plants.

Detailed cytological study in the tetrasomics of Coix gigantea Koen. ex Roxb. (Poaceae) has been carried out revealing a possibility of wider range in the gametic constitution than is generally predicted through breeding experiments. Although majority of the PMCs showed nine bivalents and a quadrivalent association at diakinesis, the four homologues gave two bivalents, bivalent and two univalents, trivalent and a univalent and rarely four univalents. Orientation and segregation in all these associations, especially irregularities involving quadrivalent and univalent, have resulted in gametes with from n=9 (n-1) to n=13 (n+3) chromosomes. There is every reason to believe that gametes up to n+2 (n=12) constitution are functional since polysomics, pentasomic (2n+3, 2n=23) and hexasomic (2n+4, 2n=24), have been isolated and cytologically studied by us in the past.

A method of studying somatic chromosomes from the leaf sheath meristem-intercalary meristem-of some genera of tribe Maydeae (Poaceae) has been described. The procedure outlined to bring out chromosomes from leaf sheath is simple and yields well-spread clear somatic chromosome complements for karyotype studies. The technique can be extended to all grasses with equally good results and could be found useful in chromosomal screening of a population.