This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Another monotypic Japanese genus. A deciduous shrub with opposite branches and leaves, and rather large white flowers. Calyx-lobes 4, large, foliaceous, deeply serrated. Petals 4. Stamens many. Carpels 1 to 4, drupoid, brown, shining, 1-seeded, putamen bony. Name from a rose, and a type.