Gymnanthemum Cass., 1817

Robinson, Harold, Skvarla, John J. & Funk, Vicki A., 2016, Vernonieae (Asteraceae) of southern Africa: A generic disposition of the species and a study of their pollen, PhytoKeys 60, pp. 49-126 : 68-70

Gymnanthemum Cass., 1817 Figures 9 A–D ; 10 A–E

Gymnanthemum Cass. Bull. Soc. Philom. Paris 1817: 10. 1817. - Type: Gymnanthemum cupulare Cass. = Baccharis senegalensis = Gymnanthemum coloratum (Willd.) H. Rob. & B. Kahn

Bracheilema R. Br. ex Salt., Abyss. Append. 65. 1814, nom. nud.

Decaneurum DC., Arch. Bot. (Paris) 2: 516. 1833, nom. superfl., type same as Gymnanthemum .

Plectreca Rafin., Fl. Tellur. 4: 119. 1838. - Type: Staehelina corymbosa Thunb.

Keringa Rafin., Sylva Tellur. 144. 1838. - Type: Vernonia amygdalina Del.

Cheliusia Sch. Bip. in Hochst., Flora 24 [Intell. 1(2)] 26. 1841, nom. nud. - Cheliusia abyssinica Sch. Bip. = Gymnanthemum amygdalinum (Del.) Sch. Bip. ex Walp.

Vernonia subsect. Urceolata S.B. Jones, Rhodora 83: 67. 1981. - Type: Vernonia sphaerocalyx O. Hoffm.

Descriptions.

Shrubs or small trees, moderately to densely branching; stems mostly terete, with solid pith; hairs of stem often forming a felt, with large often contorted cap cells basally or nearly basally attached. Leaves alternate; petioles short, winged or elongate; blades membranaceous to rather coriaceous, margins entire to serrate or repand dentate, upper surfaces essentially glabrous and somewhat glossy to arachnoid tomentose; secondary veins pinnate, spreading at 30-80° angles, arching nearer margins. Inflorescences terminal, densely corymbiform, with small bracteoles; peduncles short. Heads with campanulate to cylindrical or ovoid involucres; involucral bracts coriaceous to subcoriaceous, appressed, 25-35 in 4-5 gradate series, inner bracts persistent to easily deciduous, outer surface with smooth median shield, without narrow median costa or keel; receptacles epaleaceous. Florets 5-50 in a head; corollas white to violet, basal tube cylindrical, throat longer than the anther thecae or very deeply cut, lobes with glands or spicules on outer surface; anther thecae with base broadly tailed, tails often long; apical appendages glabrous, with rather thick-walled cells; style base without or with scarcely distinct node; style branches with stout, pointed sweeping hairs. Achenes 5-10-costate, with or without setulae, raphids short to elongate, sometimes not evident; pappus of many rather persistent capillary bristles, often with broadened tips, with outer series of short squamellae. Chromosome numbers n = 10, 15, 20 ( Jones 1970, 1982; Adegbite and Ayodele 2004).

Pollen: 30-35 μm in diam. (dry); tricolporate, echinate, sublophate; tectum continuous in intercolpi and at poles, with distinct microperforations; spines long, each with single stout columella below firmly attached to footlayer, intervening perforated tectum scarcely mamillose on inner surface (Fig. 10 A–E ).

Generic limits more restricted than given in Robinson (1999a), see Robinson and Skvarla (2006, 2007) and Robinson et al. (2008).

A special effort has been made to resolve the endemic southern African element of Gymnanthemum that includes Gymnanthemum corymbosum and Gymnanthemum capense ( Swelankomo et al. 2015).

Figures

Figure 9. Photographs of Gymnanthemum: A Gymnanthemum corymbosum (Thunb.) H. Rob. B-D Gymnanthemum capense (A. Spreng.) J. C. Manning & N. Swelankomo. See Appendix C for citation details.

Figure 10. Scanning electron micrographs of acetolyzed pollen of two collections of sublophate echinolophate Gymnanthemum capense (A. Spreng.) J. C. Manning & N. Swelankomo. A Polar view B Equatorial view C Lateral view D Fractured grain structure of exine surfaces E Fractured grain showing spine construction. (A-C Schlechter 6644).