Cytological and geographical characterizations of Hemarthria

Chromosme numbers were determined for 56 Hemarthria altissima(Poir.) Stapf et C. E. Hubb. introduction, forty of these were diploid (2n=18) and 16 were tetraploid (2n=36). These results, combined with previous findings, show that all but three of the tetraploids in the USDA Hemarthria altissima collection originated north of 20 S latitude. All other introductions collected throughout southern Africa were diploid. Meiosis was regular in a hexaploid, 6 tetraploid and 32 diploid introductions but a low frequency of quadrivalents was found in the teraploids. H. uncinataR. Br. and H. uncinata var. spathacea (Domin) Vickery were found to have 2n=36 chromosomes H. compressa (L.f.) R. Br., introduced from Japan, had 2n=54 chromosomes. No major cytological abnormalities exist in these Hemarthria species. Significant variation exists among the ploidy levels for cold tolerance and in vitro organic matter digestion to provide the basis for a forage improvement program.