Tragus (plant) explained

Tragus, commonly called bur gras, burr grass or carrot-seed grass, is a genus of plants in the grass family. It is native to Africa, Australia, and Eurasia with several species on islands in the Atlantic, Indian, and Pacific Oceans plus one species in Argentina.^{[1] [2] [3]}

Plants are monoecious, stoloniferous, and either annual or perennial depending on the species. The genus has been introduced in subtropical and tropical areas around the world as weeds of disturbed areas. The culms (stems) are ascending or low and mat forming, glabrous, and circular in cross-section. Blades are flat or folded and linear, ligules membraneous and trichomatous. Flowers are born in narrow panicles; the primary branches are spirally arranged, each possessing 2-5 spikelets; each of these spikelets bears a single floret. Each floret has 3 stamens, the anthers of which are pale yellow. The caryopses (grains) are elliptical and golden-brown.^{[4] [5] [6]}

Four species of Tragus have been introduced to North America: T. australianus, T. berteronianus, T. heptaneuron, and T. racemosus.^[7] The natural chromosome count is 2n = 20 in T. berteronianus, and 2n = 40 in T. racemosus.^[8] Tragus species utilize C₄ photosynthesis. They prevent erosion, but make for poor grazing and in larger numbers indicate overgrazing.^[9]

Species^{[10] [11]}

• Tragus andicola - Argentina (Catamarca, Jujuy, Salta, Tucuman)
• Tragus australianus - Australia, New Caledonia
• Tragus berteronianus - Africa, Arabian Peninsula, Iran, Afghanistan, Pakistan, China; introduced in North America, West Indies, South America
• Tragus heptaneuron - Somalia, Kenya, Tanzania
• Tragus koelerioides - Zimbabwe, Namibia, Botswana, Lesotho, South Africa
• Tragus mongolorum - Mongolia, China, Indian Subcontinent, Indochina, Madagascar, Mauritius, Réunion
• Tragus pedunculatus - Namibia, Botswana
• Tragus racemosus - Africa + Eurasia from France and Canary Islands to South Africa to Kazakhstan

formerly included^[10] several species now regarded as better suited to other genera: Brachypodium Bromus Festuca Leptothrium Lolium Pseudechinolaena

External links

• Plants of Hawaii Gallery: Tragus berteronianus (Non-Native)
• Flora of America: Illustration of Tragus bertonianus and T. racemosus

Notes and References

1. Haller, Albrecht von. 1768. Historia Stirpium Indigenarum Helvetiae Inchoata 2: 203
2. http://www.tropicos.org/Name/40016348 Tropicos, Tragus Haller
3. http://ausgrass2.myspecies.info/content/tragus Ausgrass2, Grasses of Australia
4. Web site: RLEM 610 grass taxonomy tragus . 2008-02-23 . 2008-05-16 . https://web.archive.org/web/20080516223328/http://www.csdl.tamu.edu/FLORA/taes/tracy/610/tragus.html . dead .
5. http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=133281 Flora of China, Vol. 22 Page 495 锋芒草属 feng mang cao shu Tragus Haller, Hist. Stirp. Helv. 2: 203. 1768.
6. http://luirig.altervista.org/flora/taxa/floraspecie.php?genere=tragus Altervista Flora Italiana, Lappola, European Bur Grass, Klettengras, Tragus à grappes, Carretes, Tragus
7. http://bonap.net/NAPA/TaxonMaps/Genus/County/Tragus Biota of North America Program 2013 county distribution maps
8. Web site: Archived copy . 2008-02-23 . dead . https://web.archive.org/web/20100626145632/http://www.herbarium.usu.edu/treatments/Tragus.htm . 2010-06-26 .
9. http://www.fao.org/AG/AGP/agpc/doc/Gbase/Safricadata/trakoel.htm Tragus koelerioides
10. http://apps.kew.org/wcsp/namedetail.do?name_id=446759 Kew World Checklist of Selected Plant Families
11. http://www.theplantlist.org/tpl1.1/search?q=Tragus The Plant List search for Tragus