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Acorus calamus var. americanus

(Calamus)

Interesting Facts

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Common Names

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Common Names in English:

Calamus

Description

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Family Acoraceae

Herbs, perennial , wetland, usually with aromatic oil , especially in rhizomes. Rhizomes horizontal, creeping at or near surface , branched. Stems repent , branched rhizomes. Cataphylls absent. Leaves not differentiated into petiole and blade , equitant, sword-shaped , larger than 1.5 cm; venation parallel along length of leaf. Inflorescences: spadices, from 3-angled axis (peduncle fused with proximal portion of sympodial leaf, i.e. , leaf encircling terminal inflorescence), distal sympodial leaf extending beyond spadix; true spathe absent; spadix nearly cylindric , tapering, apex obtuse . Flowers bisexual ; tepals 6; stamens 6, distinct ; ovariesy 1, (1--) 3-locular, sessile; stigmas sessile (styles essentially absent), minute. Fruits berries ; pericarp thin, leathery. Seeds 1--6(--14), from apex of locule.

Genera 1, species 3--6 (2 species in the flora ) : temperate Northern Hemisphere, tropical Asia at higher elevations , and sporadically introduced into Southern Hemisphere.

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.[1]

Genus Acorus

Herbs, wetlands or rocky stream banks, when bruised or broken producing pleasant and distinctive aromatic odor. Leaves bright green; sheathing base 2-facial (proximal part of leaf) ; distal part of leaf 1-facial, flattened in median rather than transverse plane ; prominent veins 1--6, parallel along length of leaf. Inflorescences solitary. Flowers: tepals light brown; anthers yellow, introrse ; ovariesy green. Fruits light brown to reddish with darker streaks. Seeds embedded in mucilage. x = 12.

Species 3--6: temperate Northern Hemisphere, tropical Asia at higher elevations , sporadically introduced in Southern Hemisphere.

Considerable confusion exists in the taxonomic literature over the status of Acorus in North America. Whether Acorus is native or introduced, as well as the number of taxa in North America, has been debated for years. Evidence based on studies of morphology, essential oil chemistry, cytology , isozymes , and ethnobotany supports the existence of two species in North America”A. calamus, an introduced sterile triploid, and A. americanus, a native fertile diploid (J. G. Packer and G. S. Ringius 1984; S. A. Thompson 1995). Acorus americanus is not only morphologically distinct from triploid A. calamus but also from diploid and tetraploid A. calamus populations occurring in Asia (L. C. M. Röst 1979; S. A. Thompson 1995). Although the existence of two species of Acorus in North America was discussed by J. G. Packer and G. S. Ringius (1984) and A. americanus has been listed in several North American floras , this is the first flora that formally treats two species of Acorus in North America and provides a key to distinguish these two species.

Traditionally, the name Acorus calamus has been applied to all populations of Acorus in North America without regard for the biological species involved. Other authors (e.g. , E. T. Browne and R. Athey 1992; K . A. Wilson 1960) have adopted A. americanus as the "correct" name for all Acorus in North America, including populations in regions where only A. calamus occurs or is the predominant species. The use of either name in the literature requires further study to determine which species is being cited.

The rhizomes of Acorus calamus contain an aromatic oil that has been used medicinally since ancient times and has been harvested commercially. Native Americans exploited Acorus as a medicine and for ceremonial uses. Although this plant is cited in the ethnographic and ethnobotanical literature as A. calamus, the distribution of the tribes reported to use Acorus corresponds to the range of the native species (S. A. Thompson 1995).

The combination of equitant, sword-shaped leaves plus an elongate inflorescence borne about midway on a sympodial leaf is not found in any other North American plant. Fresh material of Acorus is easily distinguished from other plants by the unique pleasant fragrance given off by rhizomes and leaves when broken. The bright green color of the leaves is also distinctive.[2]

Taxonomy

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Synonyms

Acorus americanus (Raf.) Raf.

Notes

Name Status: Accepted Name .

Last scrutiny: 11-Nov-2003

Similar Species

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Members of the genus Acorus

ZipcodeZoo has pages for 16 species, subspecies, varieties, forms, and cultivars in this genus:

A. calamus (Sweet Flag) · A. calamus var. americanus (Calamus) · A. calamus 'Variegatus' (Variegated Sweet Flag) · A. gramineus (Grassleaf Sweet Flag) · A. gramineus 'Argenteastriatus' (Grassy-Leaved Sweet Flag) · A. gramineus 'Golden Pheasant' (Grassy-Leaved Sweet Flag) · A. gramineus 'Hakuro-Nishiki' (Grassy-Leaved Sweet Flag) · A. gramineus 'Himemasamune' (Grassy-Leaved Sweet Flag) · A. gramineus 'Licorice' (Grassy-Leaved Sweet Flag) · A. gramineus 'Masamune' (Grassy-Leaved Sweet Flag) · A. gramineus 'Minimus Aureus' (Grassy Leaved Sweetflag) · A. gramineus 'Oborozuki' (Grassy-Leaved Sweet Flag) · A. gramineus 'Ogon' (Dwarf Golden Sweetflag) · A. gramineus 'Pusillus Minimus Aureus' (Dwarf Goldensweet Flag) · A. gramineus 'Tanimanoyuki' (Grassy-Leaved Sweet Flag) · A. gramineus 'Variegatus' (Dwarf Variegated Sweetflag)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Sue A. Thompson "Acoraceae". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org. [back]
  2. "Acorus". in Flora of North America Vol. 22. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 7/22/2012