Abstract: The present paper reports the chromosome numbers and karyotypes of eight species of Sect. Rhiziridium in Allium (Liaceae). The materials were all collected from their natural populations in east Inner Mongolia, China. The karyotype analysis is made on the basis of Li et al. (1985).The results are as follows (for chromosomes parameters, voucher specimens and localities, see Table 1 and Plate 1--2 the idiograms of the eight species in Fig. 1): (1) Auium leucocephalum Turcz. The somatic chromosome number and karyotype of this species is 2n=16=12m=2sm+2st (2SAT), in Stebbinsl(1971) kayotype classification, which belongs to 2A (Plate 1: 1; Fig. 1: 1). The range of chromosome relative length varies between 8.90--15.55%. Two small satellites are attached to the short arms of the 8th pair of chromosomes. (2) A. strictum Schrader has 2n (4x) =32=16m+4sm+12st, belonging to 2B (Plate 1: 2 & Fig. 1: 2). Satellites were not observed., and the range of chromosome relative length is between 3. 67-11.00%. (3) A. ramosum L. 2n=16=14m+ 2st (2SAT), belonging to 2A (Plate 1: 3 & Fig. 1: 3), Two small satellies are attached to the short arms of the 8th pair of chromosomes. The range of chromosome relative length is between 9.17-16.39%. The chromosome number and karyotype of this species are in accordancewith those reported by Li et al. (1982) with the material from Jinshan, Beijing. (4) A. bidentatum Fisch. ex Prokh. 2n (4x) =32=24m+4sm+4T, belonging to 2B (Plate 1: 4 & Fig. 1: 4). Satellites were not observed. A small median B-chromosome was found in root-tip cells of the population growing in sandy soil, and it is the first discovery (Plate 2: 9). The species has terminal chromosomes, which are seldom seen in Sect. Rhiziridium. The range of chromosome relative length is between 3.32—9.06%. (5) A. tenuissimu L. 2n=16= 10m+4sm+2st(2SAT), belonging to 2B(Plate 1:5 & Fig. 1:5). Two large satellites are attached to the short arms of the 8th pair of chromosome. The range of chromosome relative length is between 8.27--17.56%. (6)A. anisopodium Ledeb. 2n = 16 = l2m +2sm + 2st (2SAT), belonging to 2A (Plate 2:7 & Fig. 1: 7). Two large satellites are attached to the short arms of the 8th pair of chromosomes. In somatic cells of some plants of this species, a small submedian B-chromosome was found (Plate 2: 10, 11). The range of chromosome relative length is between 8.05-17.08 %. (7) A. anisopodium Ledeb. var. zimmermannianum (Gilg) Wang et Tang 2n (4x)=32=24m+4sm+4st( 4SAT), belonging to 2A (Plate 1: 6 & Fig. 1: 6). Four large satellites are attached to the short arms of the 15 and 16th pairs of chromosomes. The range of chromosome relative length is between 4.45--8.35%. This variety is similar to A. anisopodium Ledeb. in morphological characters, and their karyotype formulas are also very similar. The present authors consider that the variety is an allotetraploid derived from A. anisopodium Ledeb. (8) A. condensatum Turcz. 2n=16=14m+2st (2SAT), belonging to 2B (Plate 2:8 & Fig. 1:8). Two. small satellites are attached to the short arms of the 6th pair of chromosomes. In a few individuals of this species median (M) B-chromosome was discovered, and the number is stable (Plate 2: 12). The range of chromosome relative length is between 7.64--17.07%. In short, the chromosome numbers of the species studied in the present work are found to be 2n=16 or 32, and the karyotypes belong to 2A or 2B, highly symmetrical. The karyotypes of Chinese materials of these species are mostly reported for the first time. Threespecies have B-chromosomes.

Key words: Allium, Sect. Rhiziridium, Karyotype, China