Ixeris

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Description

Herbs, annual or perennial, often rosulate. Stems ± erect, sometimes also long creeping and with erect flowering branches. Synflorescence usually corymbiform. Capitula with (12–)15–25(–40) florets. Involucre cylindric to narrowly campanulate. Phyllaries in several series, glabrous; outer phyllaries several, longest 1/4–1/2 as long as inner ones; inner phyllaries usually 8, linear-lanceolate to lanceolate, equal in length, glabrous, margin usually scarious. Receptacle naked. Florets yellow, rarely whitish or purplish. Achene brown, ± fusiform, not compressed, with 10 (5 main ribs alternating with 5 ± equal secondary ribs) very prominent ± winglike ribs, space between ribs narrowly V- or U-shaped, apex contracted or attenuate into a filiform or slender beak. Pappus white, bristles scabrid.

from: Shih C. & Kilian N. in Wu Z. Y. & al. (ed.), Flora of China 20–21: 331. 2011, Beijing & St Louis.

Distribution

Asia-Temperate: Afghanistan (Afghanistannative); Amur (Amurnative); Buryatiya (Buryatiyanative); China North-Central (Gansunative, Hebeinative, Shaanxinative, Shandongnative, Shanxinative); China South-Central (Chongqingnative, Guizhounative, Hubeinative, Sichuannative, Yunnannative); China Southeast (Anhuinative, Fujiannative, Guangdongnative, Guangxinative, Henannative, Hunannative, Jiangsunative, Jiangxinative, Zhejiangnative); Chita (Chitanative); Hainan (Hainannative); Inner Mongolia (Nei Mongolnative, Ningxianative); Irkutsk (Irkutsknative); Japan (Hokkaidonative, Honshunative, Kyushunative, Shikokunative); Kamchatka (Kamchatkanative); Khabarovsk (Khabarovsknative); Korea (North Koreanative, South Koreanative); Kuril Is. (Kuril Is.native); Manchuria (Heilongjiangnative, Jilinnative, Liaoningnative); Mongolianative (Mongolianative); Nansei-shoto (Nansei-shotonative); Ogasawara-shoto (Ogasawara-shotonative); Primorye (Primoryenative); Qinghai (Qinghainative); Sakhalin (Sakhalinnative); Taiwan (Taiwannative); Tibet (Tibetnative); Xinjiang (Xinjiangnative); Yakutskiya (Yakutskiyanative) Asia-Tropical: Assam (Assamnative, Manipurnative, Meghalayanative, Nagalandnative); Bangladesh (Bangladeshnative); Cambodia (Cambodianative); East Himalaya (Bhutannative, Darjilingnative); India (Biharnative, Punjabnative, Uttar Pradeshnative, West Bengalnative); Laos (Laosnative); Malaya (Peninsular Malaysianative); Myanmar (Myanmarnative); Nepal (Nepalnative); Pakistan (Pakistannative); Philippines (Philippinesnative); Thailand (Thailandnative); Vietnam (Vietnamnative); West Himalaya (Himachal Pradeshnative, Jammu-Kashmirnative, Uttaranchalnative) Northern America: Delaware (Delawareintroduced); New Jersey (New Jerseyintroduced); New York (New Yorkintroduced); Pennsylvania (Pennsylvaniaintroduced)

Systematics

Ixeris is a genus centred in E Asia and extending to S and SE Asia. Originally created by Cassini to accommodate the SE Asian I. polycephala, later Gray (1859) added several similar E Asian species to it. Bentham (1873), however, merged it into Lactuca as a section, a treatment followed by most workers until Nakai (1920) again treated Ixeris as a separate genus. Nakai (1920) also split some of the E Asian species into two segregate genera, Crepidiastrum and Paraixeris. Stebbins (1937) agreed with Nakai (1920) in the separation of Ixeris from Lactuca, but did not follow him in the segregation of Crepidiastrum and Paraixeris.

A taxonomic revision of Ixeris and its relatives was provided by Pak & Kawano (1992), in particular based on carpological and cytological investigations (Pak & Kawano 1990a, b, c). Pak & Kawano's circumscription of Ixeris largely corroborates the narrow genus concept of Nakai (1920) and recently has been corroborated itself in molecular phylogenetic analyses of subtribe Crepidinae by J. W. Zhang & al. (in prep.). In this circumscription, which is followed here, Ixeris comprises close to ten species characterised by a basic chromosome number of x =8, fusiform, uncompressed achenes with 10 ± equal, very prominent, ± winglike ribs, the space between which is narrowly v- or u-shaped, and an apex contracted or attenuate into a filiform or slender beak.


References


Bentham G. 1873: Compositae. – Pp. 163-533 in: Bentham G. & Hooker J. D., Genera plantarum 2. – London: Reeve.

Gray A. 1859: Diagnostic characters of new species of phanerogamous plants, collected in Japan by Charles Wright. – Mem. Amer. Acad. Arts, ser. 2, 6: 377-452 [Ixeris: pp. 395-398].

Nakai T. 1920: Notulae ad plantas Japoniae et Koreae, XXIII. – Bot. Mag. (Tokyo) 34: 147-158.

Pak J.-H. & Kawano S. 1990a: Biosystematic studies on the genus Ixeris and its allied genera (Compositae-Lactuceae) I. Fruit wall anatomy and its taxonomic implications. – Acta Phytotax. Geobot. 41: 43-60.

Pak J.-H. & Kawano S. 1990b: Biosystematic studies on the genus Ixeris and its allied genera (Compositae; Lactuceae) II. Karyological analyses. – Cytologia 55: 553-570.

Pak J.-H. & Kawano S. 1990c: Biosystematic studies on the genus Ixeris and its allied genera (Compositae - Lactuceae) III. Fruit wall anatomy and karyology of Crepidiastrum and Paraixeris, and their taxonomic implications. – Acta Phytotax. Geobot. 41: 109-128.

Pak J.-H. & Kawano S. 1992: Biosystematic studies on the genus Ixeris and its allied genera (Compositae; Lactuceae) IV. Taxonomic treatments and nomenclature. – Mem. Fac. Sci. Kyoto Univ., Ser. Biol. 15: 29-61.

Stebbins G. L. 1937: Critical notes on the genus Ixeris. – J. Bot. 75: 43-51.

Common names

Chinese (China): 苦荬菜属 ku mai cai shuA

Chromosome numbers

Diploids, triploides, tetraploids, pentaploids, hexaploids, heptaploids, octoploids; x = 8.
B

Bibliography

A. Wu & al., Flora of China 20-21. 2011
B. Watanabe K., Index to chromosome numbers in Asteraceae.