This is a report on chromosome numbers for 14 species of the subtribe Aveninae. which is largely naturalized in South Africa. This is the first chromosome number report for Helictotrichon longifolium (Nees) Schweick. (n = 14). H. longum (Stapf)Schweick. (n = 14). H. namaquensis Schweick. (n = 14) and Lophochloa cristata (L.) Hyl. (n = 7, 21/2. 14). The subtribe has a basic chromosome number of seven, and fewer ploidy levels occur in the naturalized species in South Africa than in the same species in other parts of the world. All tetraploid specimens were alloploids.

The genus Chaetobromus consists of four, somewhat ill defined species. Morphological merging and the existence of intermediates render the separation of these species difficult. A basic chromosome number of x = 6 for Chaetobromus is substantiated by the presence of diploid specimens. The genus forms a polyploid complex, ranging from diploid to duodecaploid. Polyploidy occurs in the form of segmental alloploidy and occasionally as alloploidy. Meiotic abnormalities, in the form of univalents during metaphase I and anaphase laggards, were observed in some specimens. A cancerous growth form, involving the merging of different cells and the subsequent fusion of their nuclei, has been observed in two specimens, Spies 3366 and CW1. No apparent explanation could be found for this uncontrolled increase in ploidy level during microsporogenesis. Extensive morphological, anatomical, and cytogenetical variation exists in the genus, indicating hybridization and polyploidization. Numerical analysis of morphological data obtained from the specimens studied indicates two groups. Cytogenetic evidence supports the numerical analysis. In an attempt to resolve the contributor species to this polyploid hybrid swarm, attention should be given to the diploid representatives of the putative progenitor species.Key words: Chaetobromus, hybridization, meiosis, numerical taxonomy, polyploidy.

No abstract

Representative specimens of various species of the genera  Andropogon L.,  Cymbopogon Spreng.,  Elionurus Kunth ex Willd.,  Hyparrhenia Foum. and  Hyperthelia Clayton were cytogenetically studied. All specimens had a secondary basic chromosome number of ten. Polyploidy, either as alloploidy or segmental alloploidy. was frequent. The taxa studied represent mature polyploid complexes.

This is a report on chromosome numbers for the tribe Poeae, which is represented in South Africa mainly by naturalized exotics. Chromosome numbers of 67 specimens, representing 26 species and 11 genera, are presented. These numbers include the first reports on Poa binata Nees (n = 3x = 21 and n = 4x = 28), Puccinellia acroxantha C.A.Sm. CE.Hubb. (n = 3x = 21) and P. angusta (Nees) C.A.Sm. C.E.Hubb. (n = x = 7). New ploidy levels are reported for Catapodium rigidum (L.) CE.Hubb.(n = 2x = 14), Festuca caprina Nees (n = 2x = 14) and F. scabra Vahl (n = x = 7).

Bothalia 32,1: 1 2 3 -1 2 6 (2 002) Miscellaneous notes POACEAE CHROMOSOME STUDIES ON AFRICAN PLANTS. 16. POLYPLOIDY IN THE GENUS EHRHARTAThe genus Ehrharta Thunb. comprises ± 36 species of which 20 are endemic to the winter rainfall area of South Africa (Verboom 2000). The genus belongs to the tribe Ehrharteae, which has been shuffled betw een the Phalarideae and the O ryzeae, the Ehrharteae and Arundineae of the Arundinoideae, the Ehrharteae of the Oryzoideae, and the Ehrharteae and the Oryzaneae of the Bambusoideae (Gibbs Russell & Ellis 1987). Recently the Ehrharteae was moved from the Arundinoideae (Renvoize 1981) to the Bambusoideae (Renvoize 1985; Watson et al. 1985). Linder & Ellis (1990) found no other representatives of the Bambusoideae present in the Fynbos Biome. Inclusion of the tribe Ehrharteae in the Bambusoideae rests on the presence of non-anatomical characters such as bambusoid embryos and lodicules (Renvoize 1985; Clayton & Renvoize 1986). Currently the E hrharteae form s part o f the 'B EP' clade (Bambusoideae, Ehrhartoideae and Pooideae) in grass phylogenetics (Clark et al. 1995).The presence of many endemic species and the absence of any close relatives to Ehrharta in South Africa, may present us with some answers to the forma tion of polyploidy in grasses. Polyploidy is a common phenomenon among the grasses and Stebbins (1985) sug gested that more than 80% of species in this family have undergone some form of polyploidy somewhere in their evolutionary history. In an attempt to determine the degree of polyploidy in South African grasses, our labora tory has studied chromosome numbers of various grasses and the results were mostly published in this series.One of the genera that has been extensively studied, is the genus Ehrharta. Various chromosome number reports for the genus Ehrharta have been published (Avdulov 1931;Nakamori 1933: Parthasarathy 1939Love 1948;Stebbins 1949: Raven et al. 1965Tateoka 1965: Fernandes & Queiros 1969: Stebbins 1985Spies & Du Plessis 1986: Hoshino & Davidse 1988 Spies & Voges 1988; Spies et al. 1989). This report includes additional results from collections from 37 populations, representing nine different species or subspecies and includes first counts for three species and one subspecies. These new counts are combined with the published results (in total more than 100 specimens have been studied) in an attempt to determine the degree of polyploidy within this genus.

CHROMOSOME STUDIES ON AFRICAN PLANTS. 14. PANICOIDEAE

CHROMOSOME STUDIES ON AFRICAN PLANTS. 12. THE TRIBES OF SUBFAMILY POOIDEAE