The family was formerly sometimes treated to include the hackberries, (Celtis and allies), but an analysis by the Angiosperm Phylogeny Group suggests that these genera are better placed in the related family Cannabaceae.[4] It generally is considered to include ca 7 genera and about 45 species.[5] Some classifications also include the genus Ampelocera.[6]
Description
The family is a group of evergreen or deciduous trees and shrubs with mucilaginous substances in leaf and bark tissue. Leaves are usually alternate on the stems. The leaf blades are simple (not compound), with entire (smooth) or variously toothed margins, and often have an asymmetrical base. The flowers are small and either bisexual or unisexual.[7] The fruit is an indehiscent samara, nut, or drupe.
^ abUeda, Kunihiko; K Kosuge; H Tobe (June 1997). "A molecular phylogeny of Celtidaceae and Ulmaceae (Urticales) based on rbcL nucleotide sequences". Journal of Plant Research. 110 (2): 171–178. Bibcode:1997JPlR..110..171U. doi:10.1007/BF02509305. S2CID38413808.
^ abSytsma, Kenneth J.; Morawetz, Jeffery; Pires, J. Chris; Nepokroeff, Molly; Conti, Elena; Zjhra, Michelle; Hall, Jocelyn C. & Chase, Mark W. (2002), "Urticalean rosids: Circumscription, rosid ancestry, and phylogenetics based on rbcL, trnL–F, and ndhF sequences", Am J Bot, 89 (9): 1531–1546, doi:10.3732/ajb.89.9.1531, PMID21665755, S2CID207690258
^Neubig K, Herrera F, Manchester S, Abbott JR (July 7–11, 2012). Fossils, biogeography and dates in an expanded phylogeny of Ulmaceae. Botany 2012: Annual Meeting of the Botanical Society of America in Columbus, Ohio, USA. St. Louis, Missouri: Botanical Society of America. Abstract 316.
