Tripleurospermum Schultz-Bip.
Tripleurospermum is a genus with ca. 40 species in Eurasia with some species extending to North America and North Africa. It has often been included within Matricaria. It is distinguished from the latter by its 3-ribbed cypselas bearing two abaxial resinous glands (Bremer & Humphries 1993). Oberprieler (2001) showed that, despite the absence of receptacular scales, it is fact more closely related to Anthemis s.str. than it is to Matricaria. With, among others, Anthemis, Cota and Tanacetum it belongs to Anthemidinae, while Matricaria is a member of Matricariinae (Oberprieler & al. 2007). A single species with two subspecies (two distinct species according to many authors) is native in Belgium: Tripleurospermum maritimum (L.) Koch (Lambinon & Verloove 2012, sub Matricaria).
The presence of mature cypsela is often necessary for an accurate identification of species of Tripleurospermum. Even then, it remains a taxonomically complex genus.
1 Capitula disciforme, ligules absent or vestigial === Tripleurospermum decipiens
Capitula radiate, with distinct white ligules (native) === T. maritimum
Literature:
Applequist W.L. (2002) A reassessment of the nomenclature of Matricaria L. and Tripleurospermum Sch. Bip. (Asteraceae). Taxon 51(4): 757-761.
Bremer K. & Humphries C.J. (1993) Generic monograph of the Asteraceae-Anthemideae. Bull. Nat. Hist. Mus., London 23(2): 1-177.
Hamet-Ahti L. (1967) Tripleurospermum (Compositae) in the northern parts of Scandinavia, Finland and Russia. Acta Bot. Fenn. 75: 1-19.
Hossain E. (1973) Materials for a flora of Turkey: 29. Tripleurospermum Schultz Bip. Notes Roy. Bot. Gard. Edinburgh 32. (2): 251-254.
Hossain E. (1975) Tripleurospermum. In Davis P.H. (ed.), Flora of Turkey and the East Aegean Islands, vol. 5. Edinburgh: Edinburgh University Press: 295-311.
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Oberprieler C. (2001) Phylogenetic relationships in Anthemis L. (Compositae, Anthemideae) based on nrDNA ITS sequence variation. Taxon 50: 745-762.
Oberprieler C., Himmelreich S. & Vogt R. (2007) A new subtribal classification of the tribe Anthemideae (Compositae). Willdenowia 37: 89-114. [available online at: http://www.bgbm.org/sites/alienplantsbelgium.bedefault/files/documents/wi37-1Oberprieler%2Bal.pdf]
Pobedimova E.G. (1995). Tripleurospermum. In: Shiskin B.K. & Bobrov E.G. (eds.), Flora U.S.S.R., vol. 26. Bishen Singh Mahendra Pal Singh and Koeltz Scientific Books: 152-177. [available online at: http://www.biodiversitylibrary.org/item/94981#page/7/mode/1up]
Podlech D. (1986) Tripleurospermum. In Rechinger K.H.. f. (ed.), Flora Iranica, vol. 158, Graz: Academische Druck und Verlagsanstalt: 73-80.
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