4a. Rosaceae Jussieu subfam. Rosoideae Arnott, Botany. 107. 1832.
Herbs, shrubs, or subshrubs. Leaves alternate, rarely opposite, pinnately compound, sometimes simple or palmately compound; stipules present, rarely absent. Flowers: torus usually enlarged, sometimes small or absent; carpels 1–260(–450), distinct, free, styles distinct, rarely connate (Roseae); ovules 1(or 2), collateral (Rubeae) or superposed (Fallugia, Filipendula). Fruits achenes or aggregated achenes ˂sometimes with fleshy, urn-shaped hypanthium or enlarged torus˃, sometimes aggregated drupelets; styles persistent or deciduous, not elongate (elongate ˂but not plumose˃ in Geum). x = 7(8).
Tribes 6, genera 28–35, species ca. 1600 (6 tribes, 26 genera, 302 species, including 1 hybrid, in the flora): North America, Mexico, West Indies, Bermuda, Central America, South America, Eurasia, Africa, Atlantic Islands, Indian Ocean Islands, Pacific Islands, Australia.
Variation in the number of genera in subfam. Rosoideae is due to differences in generic delimitation between D. Potter et al. (2007) and the authors of some Potentilleae genera. Cyanogenic glycosides and sorbitol are absent in the subfamily.
SELECTED REFERENCES Eriksson, T. et al. 1998. Phylogenetic analysis of Potentilla using DNA sequences of nuclear ribosomal internal transcribed spacers (ITS), and implications for the classification of Rosoideae (Rosaceae). Pl. Syst. Evol. 211: 155–179. Eriksson, T. et al. 2003. The phylogeny of Rosoideae (Rosaceae) based on sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA and the trnL/F region of chloroplast DNA. Int. J. Pl. Sci. 164: 197–211.