Cytotaxonomy of the Genus Polygonatum (Liliaceae)

1. The chromosome number and karyotype of distinct North American Polygonatum species, i.e., P. pubescens and P. commutatum, were studied cytologically on Wisconsin material.2. All P. pubescens plants proved to be diploid with 2n=20 chromosomes, with their karyotype referable to the latifolium-type previously described by Therman (1950).3. Two different clones of P. commutatum were examined, viz., one each of the “typical” and “giganteum” type. Both were tetraploid with 2n=40 chromosomes, with the nearly identical karyotypes characterized by three pairs of chromosomes (Nos. 3, 4 and 8) with a secondary constriction.4. On the basis of chromosome morphology, the tetraploid P. commutatum is nearly identical to a double P. pubescens (i.e. the latifolium-type) except that the characteristic chromosome pair 4 of P. pubescens is only once represented in the tetraploid karyotype (pair 8), its mate (pair 7) lacking the secondary constriction.5. The basic karyotype of the Wisconsin tetraploid plants of P. commutatum is not clearly referrable to the latifolium-type, as one would expect on the basis of simple doubling, although it was reported as such by Therman.6. The possibility need not be excluded that P. commutatum has a different basic karyotype.