Cytogenetic studies in some representatives of the subfamily Pooideae ( Poaceae ) in South Africa . 2 . The tribe Aveneae , subtribes Phalaridinae and Alopecurinae

This is a report on chromosome numbers for the subtribes Phalaridinae and Alopecurinae (tribe Aveneae) which are. to a large extent, naturalized in South Africa. Chromosome numbers of 34 specimens, representing nine species and four genera, are presented. These numbers include the first report on Agrostis avenacea Gmel. (n = 4x = 28). New ploidv levels are reported for Phalaris aquatica L. (n = x = 7), Agrostis barbuligera Stapf var. barbuligera (n = 2x = 14 and n = 4x = 28) and A. lachnantha Nees var. lachnantha (n = 3x = 21).


INTRODUCTION
The first paper in this series on chromosome num bers of representatives of the tribe Aveneae in South Af rica, indicated the importance of determining the ploidy levels and basic chromosome numbers of naturalized and endemic flora in South Africa (Spies et al. 19%).This second paper in the series is restricted to the subtribes Phalaridinae and Alopecurinae.
The aim of this study was to determine the chromo some numbers, polyploid levels and meiotic chromosome behaviour of the South African representatives of the tribe Aveninae.These results will eventually be compared with results of indigenous and endemic taxa to compare the frequency of polvploidv between indigenous and intro duced grasses.

MATERIALS AND METHODS
The material was either collected and fixed in the field, or living material was collected in the field and planted in the nurseries of either the Department of Botany and Genetics, University of the Orange Free State (Bloemfon tein), or the National Botanical Institute (Pretoria), where the cytogenetic material was collected and fixed.The ma Anthers were squashed in aceto-carmine and meiotically analysed (Spies et al. 1996).Chromosome numbers are presented as haploid chromosome numbers to conform to previous papers on chromosome numbers in this journal (Spies & Du Plessis 1986).These numbers were compared with results published in the chromosome atlasses of Fe dorov (1969), Ornduff (1967Ornduff ( -1969)), Moore (1970Moore ( -1972Moore ( , 1974Moore ( , 1977)), Goldblatt (1981Goldblatt ( , 1983Goldblatt ( , 1985Goldblatt ( , 1988) ) and Goldblatt & Johnson (1990. 1991, 1994).Genome homol ogy was determined in some tetraploid specimens accord ing to the models described by Kimber & Alonso (1981).

RESULTS AND DISCUSSION
The subtribe Phalaridinae Rchb.consists of three gen era, of w hich two are represented in South Africa (Clayton & Renvoize 1986)   ( Goldblatt 1981Goldblatt , 1983Goldblatt , 1985Goldblatt , 1988;;Goldblatt & Johnson 1990, 1991, 1994).In addition to these numbers based on x = 5, three reports of n = 28 for A. borii, therefore x = 7, have been published (Goldblatt 1981(Goldblatt ,1985(Goldblatt ,1988)).With only three reports suggesting a basic chromosome number of seven rather than the five indicated in 55 other reports, we suggest that the basic chromosome number of the ge nus Anthoxanthum is five, as our research indicates.How ever, a re-investigation of this genus will help to clarify the position of A. borii in the genus.
Three species of the genus Phalaris were included in this study (Table 1).The only specimen of P. aquatica investigated, had both diploid (n = x = 7) and tetraploid (n = 2x = 14) chromosome numbers (Figure 1A, B).We attribute this apparent discrepancy to cell fusion (Spies & Van Wyk 1995).This process involves the formation of polynucleate microspores after cell fusion and the conse quent formation of polyhaploid pollen.This phenomenon is frequently observed in grasses and was discussed by Spies & Van Wyk (1995).Phalaris aquatica was repre sented by a diploid specimen (n = x = 7) in this study.This is a lower chromosome number than the tetraploid one previously described (Moore 1971;Goldblatt 1983Goldblatt , 1988)).Meiosis was normal at both ploidy levels with only bivalents observed.
One specimen of P minor was diploid (Figure 1C, D) and the rest (10 specimens) tetraploid (Figure 1F-H ploidy levels octoploid specimens (n = 4x = 28) have also been described in the literature (Moore 1977).The pres ence of diploid and possibly allotetraploid specimens in the same species, should render a morphological study of this species worthwhile.
. Meiosis was normal and only bivalents were formed in all specimens.The two genera representing the subtribe Phalaridineae appear to have two different basic chromosome numbers, i.e.Anthoxanthum with five and Phalaris with both six and seven.A thorough phylogenetic study based on mo lecular data of this subtribe could be very useful in de termining the evolutionary significance of the change in chromosome number.A basic chromosome number of seven is present in all the genera of the subtribe Alopecuri nae present in South Africa.
. The genus Anthoxanthum consists of 18 species, four of which are endemic to South Africa [A.

viously described by us (Spies & Du Plessis 1986). Meio- sis was normal in almost all specimens, excepting one telophase II cell of A. barbuligera, where micronuclei were observed (Figure 2C). Ammophila Host is a north temperate genus with two species, with A. arenaria (L.) Link naturalized in South Africa (Gibbs Russell et al. 1990). Although this species was not represented in this study, all reports indicate that representatives from the rest of the world are tetraploid 2n = 4x = 28
Photomicrographs of meiotic chromosomes in the genus Phalaris.A, B, P. aquatica.Spies 3676, diplotene/diakinesis with 7u and 14» respectively; C, P. minor, Davidse 33272, diakinesis with 7»; D, P. paradoxa, Spies 5395, anaphase I with 7 chromosomes in each pole; E, P minor, Spies 4593, late anaphase I with a chromatid bridge; F, P. minor, Spies 4284.diakinesis with 14»; G, P. minor.Spies 4978, metaphase I with 14ii; H, P. minor, Davidse 33237, metaphase I with 14».Scale bar: 10/xm.