Washington Flora Checklist
A Checklist of the Vascular Plants of Washington State
Hosted by the University of Washington Herbarium


Checklist » Acoraceae
Acoraceae   (Sweet Flag Family)

Notes: FNA22: "Acorus historically was recognized as an aberrant genus within Araceae, but much evidence supports its treatment as a separate family and the removal of this family from Arales (M. H. Grayum 1987). Other than the absence of a close association with Arales, the phylogenetic affinities of Acoraceae remain unclear. Evidence based on DNA sequences fails to show any close relationships between Acorus and other genera, and instead supports Acorus as the oldest extant lineage of monocotyledons (M. R. Duvall et al. 1993).

The removal of Acorus from Araceae is supported by the absence of a spathe and the unique vasculature of the structure traditionally interpreted as a spathe (T. S. Ray 1987). The structure that has been called a spathe in Acorus is not morphologically equivalent to the spathe of Araceae; instead it is interpreted as the distal part of the sympodial leaf. The proximal part of the sympodial leaf is adnate to the peduncle, forming a 3-angled axis that bears the inflorescence.

Family Synonyms:
» Araceae in part

» Grayum, M. H. 1987. A summary of evidence and arguments supporting the removal of Acorus from the Araceae. Taxon 36: 723--729.

Thompson, S. A. 1995. Systematics and Biology of the Araceae and Acoraceae of Temperate North America. Ph.D. dissertation. University of Illinois. Urbana-Champaign.

Family treatment authored by Peter F. Zika; last updated 12/24/2009 by David Giblin
Taxon (native species in boldface) # Synonyms Common Names
Acorus americanus (Raf.) Raf.   [FNA22] 3 American sweetflag, several-vein sweetflag
Acorus calamus L.   [FNA22] 0 sweet flag

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