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Axyris caucasica

Interesting Facts

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Description

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Family Amaranthaceae

Herbs, clambering subshrubs , shrubs , or lianas. Leaves alternate or opposite, entire, exstipulate . Flowers small, bisexual or unisexual , or sterile and reduced, subtended by 1 membranous bract and 2 bracteoles, solitary or aggregated in cymes. Inflorescences elongated or condensed spikes (heads ), racemes , or thyrsoid structures of varying complexity. Bracteoles membranous or scarious . Tepals 3-5, membranous, scarious or subleathery, 1-, 3-, 5-, or 7(-23) -veined. Stamens as many as tepals and opposite these, rarely fewer than tepals; filaments free , united into a cup at base or ± entirely into a tube , filament lobes present or absent, pseudostaminodes present or absent; anthers (1- or) 2-loculed, dorsifixed , introrsely dehiscent . Ovary superior, 1-loculed; ovules 1 to many; style persistent , short and indistinct or long and slender; stigma capitate, penicillate , 2-lobed or forming 2 filiform branches. Fruit a dry utricle or a fleshy capsule, indehiscent, irregularly bursting, or circumscissile. Seeds lenticular , reniform , subglobose, or shortly cylindric , smooth or verruculose .

About 70 genera and 900 species: worldwide; 15 genera (one introduced ) and 44 species (three endemic, 14 introduced) in China.

Morphology of the androecium, perianth (tepals), and the inflorescence has traditionally been used to circumscribe genera and tribes . Pseudostaminodia are interstaminal appendages with variously shaped apices. Filament appendages are the lateral appendages of filaments (one on each side) . The basic structure of the inflorescence is the cyme (branchlets arising from the bracteole axils, the bracteoles serving as bracts for upper flowers), which can be reduced to one flower with two bracteoles and a bract. Units of dispersal vary considerably (capsules opening with lower part persistent, flower and bracteoles falling together, or cymose partial inflorescences breaking off above bract) and can be characteristic for genera. Several genera possess long trichomes serving dispersal at the base of the tepals.[1]

Genus Axyris

Herbs, annual , monoecious, covered with rusty-colored, stellate , and whitish simple trichomes . Stems ascending , not jointed or armed , slender. Leaves alternate, petiolate ; blade ovate-lanceolate to narrowly lanceolate, base tapered, margins entire, plane or revolute , apex acute to acuminate. Inflorescences glomerules , cymes, or flowers solitary. Staminate flowers in terminal glomerules or at end of pistillate cymes. Pistillate flowers solitary in upper leaf axils or forming cymes commingled with staminate flowers . Flowers unisexual ; staminate with perianth segments 3-5, stamens 2-5; pistillate with bracteoles 2, perianth segments 3-4, stigmas 2, filiform . Fruiting structures persistent , accrescent perianth surrounding utricle; utricles winged , obovate to cuneate, laterally compressed ; pericarp adherent . Seeds vertical , ovoid ; seed coat grayish, granular ; embryo horseshoe-shaped; perisperm copious . x = 9.

Species ca. 5: introduced ; Eurasia .[2]

Taxonomy

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Similar Species

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Members of the genus Axyris

ZipcodeZoo has pages for 1 species, subspecies, varieties, forms, and cultivars in this genus:

A. amaranthoides (Russian Pigweed)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Bojian Bao, Thomas Borsch & Steven E. Clemants "Amaranthaceae". in Flora of China Vol. 5 Page 415. Published by Science Press (Beijing) and Missouri Botanical Garden Press. Online at EFloras.org. [back]
  2. Leila M. Shultz "Axyris". in Flora of North America Vol. 4 Page 260, 308. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 7/26/2012