Orbivestus H. Rob., 1999

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 : 84-87

Orbivestus H. Rob., 1999 Figures 17 C–E ; 19 A–G

Orbivestus H. Rob., Proc. Biol. Soc. Wash. 112(1): 230. 1999. - Type: Vernonia karaguensis Oliv. & Hiern.

Vernonia subg. Orbisvestus S.B. Jones, Rhodora 83: 60. 1981. - Type: Vernonia karaguensis Oliv. & Hiern.

Descriptions.

Subshrubs to small shrubs with erect stems from a woody base, not or sparsely branched between base and inflorescence; hairs T-shaped. Leaves alternate, usually decrescent upwardly, sessile or short petiolate, blades elliptical or ovate to oblanceolate, mostly 4-9 cm long, 2-5 cm wide, base short-obtuse to acuminate, margins scarcely repand-dentate, apex short-acute, upper surface with small spinules and few small hairs, lower surface paler, grayish with slender hairs and partially sunken glandular dots; venation pinnate, with up to six or eight lateral veins each side, spreading at 45 –60º angles. Inflorescences with leaves of main axis only somewhat to greatly reduced, with only minute bracteoles on branches. Inflorescence shape broadly corymbiform or cylindrical with rounded to flattened top, with lower heads appearing sessile as result of proliferation by immediately subtending branches forming seriate or scorpioid cymes, branches of inflorescence tomentose with T-shaped hairs. Heads broadly campanulate, 4-14 mm high and wide; involucral bracts mostly persistent, innermost somewhat deciduous, ca. 50-100 in 5-7 series, strongly gradate, 1-8 mm long, 1.0-1.5 mm wide, ovate to oblong, subacute and mucronate to apiculate at tip, innermost acute, tips appressed, margins membraneous and irregularly denticulate distally, often reddish, with dark median keel extending to apex, scarcely thickened and greenish near keel, with numerous small T-shaped hairs except at margins. Receptacle epaleate and tuberculate. Florets 15-ca. 50 in a head; corollas purplish, narrowly funnelform, 4-8 mm long, with sparsely scattered glandular dots, tube slender, 2-3 mm long, throat 1.5-2.5 mm long, lobes 1.0-2.5 mm long, linear-lanceolate, erect, not recurving, sparsely glanduliferous to distinctly or minutely scabridulous outside, without longitudinal internal ducts filling lobe; anther thecae 1-2 mm long, without glandular dots, calcarate and with long tails at base, endothecial cells short usually with 2-3 nodes on transverse walls; apical appendage 0.5-1.0 mm long, narrowly lanceolate, often sharply acute; style base with distinct expanded node; sweeping hairs on style branches and scarcely extending on to upper style shaft, slender and narrowly acute. Achenes 1.5-2.0 mm long when mature, 5-costate, with few to many setulae when young, often glabrous at maturity, often with numerous glandular dots on sides between costae, surface with numerous idioblasts that are not joined in series, with narrowly rhomboid raphids internally; carpopodium stopper-shaped to slightly turbinate, with many series of small thick-walled cells; inner pappus of 25-30 slender capillary bristles, rather flattened outside and barbellate on sides, tips only slightly narrowed, outer pappus of narrow scales 0.5-1.5 mm long. Chromosome numbers n = 10, 18, 20 ( Mangenot and Mangenot 1962; Bhandari and Singhvi 1977; Morton 1993).

Pollen grains ca. 50 μm in diameter in fluid, type A, sublophate, tricolporate, echinate, with perforated tectum continuous between colpi (Fig. 19 D–E ). The grains may also be somewhat asymmetrical (Fig. 19 A ).

Most notable secondary metabolites are 5-alkylcomumarins ( Bohlmann and Jakupovic 1990, as Vernoniia cinarescens Sch. Bip.) and sesquiterpene glaucolides ( Bohlmann and Jakupovic 1990, as Vernonia cistifolia O. Hoffm.).

The genus is almost alone in the eastern hemisphere in its seriate cymes, often referred to as scorpioid cymes. Such inflorescences are common in the western hemisphere Vernonieae , occurring in Vernonia itself.

Figures

Figure 17. Photographs of Oocephala and Orbivestus: A-B Oocephala centauroides (Klatt) H. Rob. & Skvarla, note: egg-shaped head C-E Orbivestus cinerascens (Sch. Bip. in Schweinf.) H. Rob. See Appendix C for citation details.

Figure 19. Scanning electron micrographs of Orvibestus cinerascens (Sch. Bip. in Schweinf.) H. Rob. A Polar view showing 3 colpi B Polar view showing 4 colpi C Lateral view showing highly perforated sheet-like layers of exine common in many grains of the sample D Equatorial view (appearing nearly echinolophate) E Lateral / equatorial view showing 2 pores F Fractured grain showing thickened columellae supporting a higher perforate surface G Fractured polar surface (A-G Koekemoer 232).