(incl. Aceraceae, Hippocastanaceae)
Molecular studies have demonstrated that Aceraceae and Hippocastanaceae are in fact nested in Sapindaceae (Harrington & al. 2005) despite being very different in appearance. Although still controversial Sapindaceae family is only monophyletic when Aceraceae and Hippocastanaceae are included (Buerki & al. 2010). Four genera have been recorded in Belgium, only one (Acer) with native representatives.
1 Herbaceous vine, climbing by tendrils === Cardiospermum
Shrubs or trees, never climbing and tendrils absent === 2
2 Leaves alternate, once or twice pinnate. Fruit an inflated capsule === Koelreuteria
Leaves opposite, simple, lobed or once pinnate (in the latter case fruit never an inflated capsule) === 3
3 Fruit composed of two winged parts (samaras), each containing one seed. Flowers in terminal corymbs or raceme-like panicles, inconspicuous. Leaves simple, variously lobed or pinnate but not palmately divided === Acer
Fruit a 3-valved capsule. Flowers in large terminal panicles, conspicuous. Leaves always palmately divided === Aesculus
Buerki S., Lowry II P.P., Alvarez N., Razafimandimbison S.G., Küpfer P., Callmander M.W. (2010) Phylogeny and circumscription of Sapindaceae revisited: molecular sequence data, morphology and biogeography support recognition of a new family, Xanthoceraceae. Plant Ecology and Evolution 143(2): 148-159. [available online at: http://www.ingentaconnect.com/content/botbel/plecevo/2010/00000143/00000...
Harrington M.G., Edwards K.J., Johnson S.A., Chase M.W. & Gadek P.A. (2005) Phylogenetic inference in Sapindaceae sensu lato using plastid matK and rbcL DNA sequences. Systematic Botany 30: 366-382.