Bothriocline Oliv. ex Benth.

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 : 57-59

Bothriocline Oliv. ex Benth. Figures 1C ; 2B ; 4 A–C

Bothriocline Hooker’s Icon. Pl. 12: 30, t. 1133. 1873. - Type: Bothriocline schimperi Oliv. & Hiern ex Benth.

Volkensia O. Hoffm., Bot. Jahrb. Syst. 20: 219. 1894; Engl. & Prantl, Natürl. Pflanzenfam. iv. 5: 387. 1893. - Type: Volkensia argentea O. Hoffm.

Resources.

Many species are keyed in Jeffrey’s (1988) treatment of Vernonieae in East Africa and in Wild and Pope (1977), Wild (1978a, 1978b).

Descriptions.

Perennial herbs (up to 1 m) to subshrubs, branching sparse, stems erect with a solid pith and long-armed T-shaped hairs with short 2-celled stalks. Leaves alternate, opposite or whorled, sessile to short petiolate, blade narrow to ovate or elliptical, pinnately veined, often paler or tomentose to sericeous below. Inflorescence laxly to densely corymbiform or thyrsiform cymes; heads pedunculate. Involucres campanulate, bracts ca. 50-60, gradate in 3-4 series, cuspidate at apex, with distinct pale or reddish lateral margins, nearly glabrous to pilosulous outside; receptacle convex, epaleaceous, with glabrous reticulum. Florets 3-100 or more in a head; corollas purplish, funnelform, basal tube slender with small stipitate glands, throat shorter than 1 mm, lobes, linear-lanceolate, with glandular dots and often with stiff subapical hairs; anther thecae blunt at base with few sterile cells; apical appendages ovate-oblong, with thin cell walls; style base with minimal annuliform node; sweeping hairs acicular, mostly restricted to branches. Achenes prismatic, short and broad with 3 –6(– 9) ribs, setuliferous with sparse short setulae scarcely split at tips, often densely covered with idioblasts and with scattered subquadrate raphids. Pappus of few or no short easily deciduous bristles narrowed at base, without obvious shorter ourter series or outer pappus a rim or collar. Chromosome number n = 9, 10, 18-20 ( Jones 1979, 1982). Pollen grains ca. 47 μm in diam, lophate to rarely sublophate, finely echinate, pores in triplet of connected colpar lacunae, perforated tectum usually restricted to muri (Fig. 4 A–C ).

Notable secondary metabolites include 5-alkylcoumarins and sesquiterpene glaucolides/hirsutanolides [ Bohlmann and Jakupovic 1990, as Bothriocline laxa N.E. Br., Bothriocline longipes (Oliv. & Hiern) N.E. Br.], and Volkesia ripensis Hutch. and 5-alkylcoumarins ( Bohlmann and Jakupovic 1990, as Erlangea fusca S. Moore, Erlangea rogersii S. Moore).

Figures

Figure 1. Photographs of Baccharoides, Bothriocline, and Vernonia potamophila. Baccharoides adoensis (Sch. Bip. ex Walp.) H. Rob. A Habit B Close up of flowering head: note that the corollas are narrowed near the apex and have an lengthened throat that is much longer than the short lobes and the involucral bracts have a differentiated margin that is often pale or reddish; Bothriocline laxa N. E. Br. C Immature heads; Vernonia potamophila Klatt. D Image of herbarium specimen (PRE). See Appendix C for citation details.

Figure 2. Illustrations: A Baccharoides adoensis (Sch. Bip. ex Walp.) H. Rob. B Bothriocline aggregata Hutch., note: this taxon is not found in southern Africa C Ethulia conyzoides L. f., note: lack of pappus; and D Gymnanthemum koekemoerae H. Rob. & V. Funk, note: broad involucral bracts without a high midrib. See Appendix C for citation details.

Figure 4. Scanning electron micrographs of acetolyzed pollen of echinolophate Bothriocline and Cyanthillium and sublophate-lophate Distephanus. A-C Bothriocline schimperi Oliv. & Hiern ex Benth. A Equatorial view, note incipient colpus of 3 connected lacunae centered on pore B Near polar view C Fractured grain D-F Cyanthillium cinereum (L.) H. Rob. D Equatorial view E Lateral view with apertures on sides F Lateral view G-I Distephanus angustifolia (DC.) H Rob. & B. Kahn. G Polar view H Equatorial view I Lateral view. (A-C, F. Meyer 8159; D-F, Evans 344; G-I, Sidley 2211).