Relationship between species in the genus Rosa, section Pimpinellifoliae

The morphology of twelve species of Rosa is described and similarities between these species are assessed. Possible origins of the tetraploid species from diploid species are indicated on grounds of comparative morphology. The wild origins of living and herbarium specimens are given in order to supplement published data on geographical distribution. Meiosis in pollen mother cells, viability of pollen grains at anthesis and ability to set seed was studied in several F₁ hybrids: no indication of complete or even partial sterility was found. Reproductive isolation is therefore unlikely to be maintained by reduced fertility of interspecific hybrids. Three species are reduced to synonymy with three other species, being retained as subspecific taxa. Two species are transferred from section Pimpinellifoliae to section Cinnamomeae.