Chromosome Counts of Carex Section Ovales

Chromosome counts for eight species of Carex section Ovales were determined (c. bebbii, C. crawfordii, C. integra, C. microptera, C. pachystachya, C. praticola, C. preslii, and C. subfusca). Combined with data from previous studies in the sect. Ovales, chromosome number variability is observed within individuals, populations, and species. Counts from 10 sib families of C. pachystachya indicate that structural rearrangements occur between generations. A total of 38 of the approximately 70 species of the section have been counted. Sixteen species have been counted more than once: seven of these show no chromosome number variation and nine have aneuploid series of numbers. Two forms of chromosome change are identified in the section: structural rearrangements and aneuploidy. At present the data cannot be used to determine whether strict aneuploidy or agmatoploidy accounts for the aneuploid variation.