[article]
| Titre : |
Some generic concepts in Compositae - Gnaphaliinae |
| Type de document : |
texte imprimé |
| Auteurs : |
O. M. Hilliard, Auteur ; B.L. Burtt, Auteur |
| Année de publication : |
1981 |
| Article en page(s) : |
pp. 181-232 |
| Langues : |
Anglais (eng) |
| Catégories : |
[Espèces (in biblio)] Gnaphalium
[Espèces (in biblio)] Helichrysum
[ZG] Afrique australe
[Thèmes] Taxonomie
|
| Résumé : |
"The species of Gnaphalium, Helichrysum and related genera in southern Africa have been surveyed and a number of groups of allied species detected in which the ratio of female to hermaphrodite flowers ranges from a majority of female to a majority of hermaphrodite and in some groups there are even homogamous species. Thus, the failure of the old sex-ratio character used to separate Gnaphalium and Helichrysum is confirmed. The validity of these groupings has been tested by studying detailed characters such as the structure of the stereome (whether undivided or fenestrated) and the type of achenial hair, as well as the more usual floral characters. Most of these plants have leaves with flat or revolute margins and the occasional occurrence of involute margins is taxonomically important.
Gnaphalium L. (type G. uliginosum L.) has been redefined to include Amphidoxa DC. and Demidium DC. (female flowers epappose) and species with more hermaphrodite flowers then female. The stereome is undivided. Helichrysum remains a massive and highly diverse genus and includes Leontonyx Cass. The stereome is normally fenestrated and the receptacle epaleate. One or two species have paleae, but Rhynea with receptacle paleate and stereome undivided is maintained. A small group of species with undivided stereomes, centred on H. marifolium D.C., has had to be retained in Helichrysum because of the existence of linking species.
Undivided stereome and subglobose achenial hairs enjoin the transfer of H. vestitum (L.) Willd. and two allies, as well as the group of species centred on H. paniculatum (Thunb.) Thunb., to Helipterum, despite the lack of plumose pappus. Edmondia Cass. (H. sesamoides (L.) Willd.) with distinctive habit, involute leaves and no close relatives in Helichrysum is reinstated.
Pseudognaphalium Kirp., to which only P. oxyphyllum (DC.) Kirp. had previously been assigned, is extended to include, in its typical subgenus, Hypelichrysum Kirp. and a number of American species of Gnaphalium, as well as the African G. undulatum L. and G. oligandrum (DC.) Hilliard & Burtt, and the Asiatic G. hypoleucum DC. and G. chrysocephalum Franch. A new subgenus, Laphangium, is created to accommodate G. luteo-album L. and its allies. Achyrocline (Less.) DC. has been maintained, as is done in South America, and some African species placed under Helichrysum by Moesert 1910) are returned to it.
Two new genera are recognized among gnaphalioid plants with undivided stereomes: Troglophyton (based on G. capillaceum Thunb.) with about seven species and Plecostachys (based on G. serpyllifolium Berg, and including G. polifolium Thunb.). Both genera straddle the old numerical boundary between Gnaphalium and Helichrysum. The monotypic Helichrysopsis Kirp. is maintained. Plants of gnaphalioid aspect with fenestrated stereomes necessitate a further new genus: Vellereophyton (type G. dealbatum Thunb., better known as G. candidissimum Lam.) with seven species. Eriosphaera Less, and Lasiopogon Cass, are redefined and enlarged to include species previously placed in Gnaphalium.
Metalasia and Lachnospermum are redefined, with the transfer of the only large-headed species remaining in Metalasia to Lachnospermum. Two new genera are created for plants in this affinity previously misplaced in Helichrysum. Atrichantha is based on H. gemmiferum Bol. and one new species is described. Dolichothrix is established for the anomalous H. ericoides (Lam.) Pers. Ifloga is briefly investigated and it is shown that the distinction between sect. Ifloga and sect. Eutrichogyne Bentham must be based on characters of the capitulum, not just on annual versus subshrubby habit. Lasiopogon molluginoides DC. (=Comptonanthus Nordenstam) is transferred to Ifloga and the structure of the capitulum in the genus is discussed.
Some earlier work on this group of plants is briefly summarized, the phytogeographical interest of the proposed arrangement is discussed and some general conclusions offered." (source : auteurs) |
| Type de publication : |
périodique |
| Référence biblio : |
Hilliard O.-M., Burtt B.-L., 1981 - Some generic concepts in Compositae - Gnaphaliinae. Botanical Journal of the Linnean Society, 82 (3) : 181-232. |
| ID PMB : |
70877 |
| Permalink : |
http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70877 |
in Botanical Journal of the Linnean Society > vol. 82, n°3 (Année 1981) . - pp. 181-232
[article]
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