Chromosome number,morphology, pairing,and DNA values of species and hybrids in the genusFallopia (Polygonaceae)

The taxa in this study have in the past been treated together in sect.Tiniaria Meissner ofPolygonum L. s.l., and more recently the large erect rhizomatous herbaceous perennials have been separated from the twining annuals and perennials as the generaReynoutria andFallopia respectively. These taxa range in ploidy level from diploid to octoploid, with base numbers of both 10 and 11 present. The plants are primarily Asiatic in distribution, although many of the large erect perennials are now naturalized in many parts of Europe. Cytological examination has revealed the presence of a number of previously unknown hybrid taxa in the British Isles. The readiness with which hybridisation occurs between taxa of differing base number and ploidy level, and similarities revealed in chromosome morphology, meiotic pairing and in DNA C-value, suggest to the authors that these two genera are best amalgamated underFallopia.